| Description | Date | Identifier | |
| Letter from AC-Sphinx regarding incorrect calibration and scale distortion on a sample speedometer, S-17281. | 4th Mar 1937 | Box 165 \ 2 img038 | |
| Letter from AC-Sphinx Sparking Plug Co. Ltd. discussing a misunderstanding over instrument specifications. | 4th Mar 1937 | Box 165 \ 2 img039 | |
| Letter from AC-Sphinx Sparking Plug Co. regarding speedometer drive cables, samples and a scheduled visit. | 4th Mar 1937 | Box 165 \ 2 img040 | |
| Letter from S. Smith & Sons regarding instrument comparisons, competitor contracts for lower horsepower cars, and A.T. policy. | 5th Mar 1937 | Box 165 \ 2 img041 | |
| Typed letter arranging a meeting to take place in Derby. | 5th Mar 1937 | Box 165 \ 2 img042 | |
| Instructions for fitting a speedometer drive to a Bentley chassis, detailing part replacements and gear ratios. | 5th Mar 1937 | Box 165 \ 2 img043 | |
| Letter from AC-Sphinx Sparking Plug Co. Ltd. to arrange a meeting regarding AC Speedometers. | 6th Mar 1937 | Box 165 \ 2 img044 | |
| Requesting the return of a Phantom III speedometer for modification to its trip mechanism. | 6th Mar 1937 | Box 165 \ 2 img045 | |
| The forwarding of a Phantom III Speedometer for modification to its trip mechanism. | 8th Mar 1937 | Box 165 \ 2 img046 | |
| Instruction to return a Bentley speedometer for modification of the tripmechanism, free of charge. | 8th Mar 1937 | Box 165 \ 2 img047 | |
| Dispatch of a Bentley Speedometer for modification of the trip mechanism. | 9th Mar 1937 | Box 165 \ 2 img048 | |
| Letter to A.C. Sphinx Sparking Plug Co. Ltd. regarding a misunderstanding over front glasses for speedometers. | 11th Mar 1937 | Box 165 \ 2 img049 | |
| Letter from AC-Sphinx Sparking Plug Co. Ltd. regarding the fitting and projection of two instrument glasses. | 13th Mar 1937 | Box 165 \ 2 img050 | |
| Modification of speedometer gears for an experimental Wraith chassis to test a special A.C. speedometer. | 15th Mar 1937 | Box 165 \ 2 img051 | |
| Letter to A.C. Sphinx Sparking Plug Co. Ltd. regarding the dispatch of two glasses. | 15th Mar 1937 | Box 165 \ 2 img052 | |
| Request to send two speedometer glasses to the A.C. Sphinx Sparking Plug Co. Ltd. | 15th Mar 1937 | Box 165 \ 2 img053 | |
| Letter to Messrs Smith & Sons requesting the cost of an electric rev counter with a circular scale. | 15th Mar 1937 | Box 165 \ 2 img054 | |
| Letter to the A.T. Speedometer Co. Ltd. requesting the introduction date of an improved speedometer drive. | 16th Mar 1937 | Box 165 \ 2 img055 | |
| Instruction to replace the speedometer on vehicle 39-EX and return the old one for overhauling. | 16th Mar 1937 | Box 165 \ 2 img056 | |
| Sending two speedometer glasses on loan to A.C. Sphinx Sparking Plug Co., Ltd. | 16th Mar 1937 | Box 165 \ 2 img057 | |
| Letter from the A.T. Speedometer Co. Ltd. concerning the supply history and design of speedometer instruments and drives. | 17th Mar 1937 | Box 165 \ 2 img058 | |
| Letter from S. Smith & Sons regarding the development and costing of an Electrical Rev. Indicator. | 17th Mar 1937 | Box 165 \ 2 img059 | |
| Requesting an examination of a faulty speedometer reported to be jumping in and out of gear. | 18th Mar 1937 | Box 165 \ 2 img060 | |
| Letter from S. Smith & Sons regarding an Electric Revolution Indicator and proposed drive lay-out ideas from Messrs. Lucas. | 30th Mar 1937 | Box 165 \ 2 img061 | |
| Letter to S. Smith & Sons regarding a decision not to proceed with an electric revolution indicator on the Lucas dynamo. | 1st Apr 1937 | Box 165 \ 2 img062 | |
| Letter from S. Smith & Sons regarding an Electric Revolution Indicator and a new combined A.T. Rev. Indicator/Electric Clock. | 2nd Apr 1937 | Box 165 \ 2 img063 | |
| Request to return a Bentley speedometer from an experimental car to its makers for modification to the trip mechanism. | 7th Apr 1937 | Box 165 \ 2 img064 | |
| Return of a Bentley Speedometer for modification to the trip mechanism. | 10th Apr 1937 | Box 165 \ 2 img065 | |
| Complaints of noisy speedometer and rev counter drives on 4¼ Bentley Chassis due to incorrect lubrication. | 14th Apr 1937 | Box 165 \ 2 img066 | |
| Change in specification for Wraith speedometers due to an alteration in tyre size. | 14th Apr 1937 | Box 165 \ 2 img067 | |
| Request to arrange for the speedometer to be removed from a Chevrolet for needle refitting. | 14th Apr 1937 | Box 165 \ 2 img068 | |
| Investigation into stiff grease used in speedometer drives supplied by Smiths. | 15th Apr 1937 | Box 165 \ 2 img069 | |
| Request for a standard Bentley speedometer and cable for a brake testing rig. | 16th Apr 1937 | Box 165 \ 2 img070 | |
| Letter from a speedometer supplier regarding noisy cables and suggestions to modify the drive to eliminate bends. | 19th Apr 1937 | Box 165 \ 2 img071 | |
| Letter from The A.T. Speedometer Co. Ltd. arranging a meeting in Derby. | 27th Apr 1937 | Box 165 \ 2 img072 | |
| Removal and replacement of the speedometer on chassis 36-EX. | 28th Apr 1937 | Box 165 \ 2 img073 | |
| Letter from AC-Sphinx Sparking Plug Co. Ltd. seeking an opinion on the Evans vane-type Fuel Pump and discussing Speedometer samples. | 28th Apr 1937 | Box 165 \ 2 img074 | |
| Letter to A.C.-Sphinx Sparking Plug Co. regarding speedometer testing and issues with Sinterkorund spark plugs. | 29th Apr 1937 | Box 165 \ 2 img075 | |
| Letter from AC-Sphinx Sparking Plug Co. Ltd. concerning speedometer work and Sinterkorund spark plug development. | 30th Apr 1937 | Box 165 \ 2 img076 | |
| Requesting the return of a Phantom III speedometer to the makers for modification. | 3rd May 1937 | Box 165 \ 2 img077 | |
| Instructions for fitting an A.C. Rev-Counter and Speedometer to a Bentley chassis for trial. | 4th May 1937 | Box 165 \ 2 img078 | |
| Return of a Phantom III speedometer for a free-of-charge modification to the trip mechanism. | 4th May 1937 | Box 165 \ 2 img079 | |
| Letter to AC-Sphinx Sparking Plug Co.Ltd. regarding the Evans Vane type fuel pump. | 5th May 1937 | Box 165 \ 2 img080 | |
| Distributing electrical specifications for petrol pumps, speedometers, and rev-counters to manufacturers for production conformity. | 19th May 1937 | Box 165 \ 2 img081 | |
| New design for Bentley Speedometer and Rev. Counter Drives to resolve service complaints. | 20th May 1937 | Box 165 \ 2 img082 | |
| The layout of the Wraith speedometer drive, referencing faults previously found on the Bentley. | 20th May 1937 | Box 165 \ 2 img083 | |
| Requesting the removal of speedometers on chassis 3-B-IV and 6-B-IV for modifications. | 27th May 1937 | Box 165 \ 2 img084 | |
| Request to replace a noisy speedometer cable on chassis 24.G.VI. | 28th May 1937 | Box 165 \ 2 img085 | |
| Request to add red radial lines to a Bentley speedometer dial to indicate maximum speeds in each gear. | 4th Jun 1937 | Box 165 \ 2 img086 | |
| Request to modify a Bentley speedometer dial with maximum speed markings for each gear. | 4th Jun 1937 | Box 165 \ 2 img087 | |
| Request to mark the maximum speeds in each gear on a Bentley speedometer dial. | 15th Jun 1937 | Box 165 \ 2 img088 | |
| Requesting the return of a speedometer for modification to its trip mechanism. | 8th Jun 1937 | Box 165 \ 2 img089 | |
| The return of a speedometer to the makers for modification. | 8th Jun 1937 | Box 165 \ 2 img090 | |
| Objections from A.T. Speedometer Co. to an electrical specification for speedometers. | 9th Jun 1937 | Box 165 \ 2 img091 | |
| Despatch of a speedometer for modification to its trip mechanism. | 9th Jun 1937 | Box 165 \ 2 img092 | |
| Performance and unreliability of A.T. speedometers. | 10th Jun 1937 | Box 165 \ 2 img093 | |
| Performance and testing of A.T. speedometers, including inertia effects and trip mechanism failures. | 11th Jun 1937 | Box 165 \ 2 img094 | |
| Letter to A.T. Speedometer Co. Ltd. requesting the delivery of two clocks for a Ph.III chassis. | 14th Jun 1937 | Box 165 \ 2 img095 | |
| Recalibration of Wraith speedometers due to a change in tyre radius. | 25th Jun 1937 | Box 165 \ 2 img096 | |
| Required recalibration of Wraith III speedometers due to a change in tyre radius. | 25th Jun 1937 | Box 165 \ 2 img097 | |
| Letter from AC-Sphinx regarding a speedometer calibration and a request for the required specification. | 29th Jun 1937 | Box 165 \ 2 img098 | |
| Letter to the AC-Sphinx Sparking Plug Co. Ltd. enclosing a copy of a speedometer specification. | 2nd Jul 1937 | Box 165 \ 2 img099 | |
| Letter to A.C. Sphinx Sparking Plug Co. Ltd. urgently requesting the return of a special Bentley speedometer after calibration. | 9th Jul 1937 | Box 165 \ 2 img100 | |
| Letter concerning the re-calibration of a special Bentley speedometer, including a table of nominal versus actual readings. | 10th Jul 1937 | Box 165 \ 2 img101 | |
| Letter from AC-Sphinx Sparking Plug Co. regarding calibration compromises on an instrument. | 10th Jul 1937 | Box 165 \ 2 img102 | |
| Request to replace the speedometer on chassis 26-G-VI and return the existing instrument for modification. | 10th Jul 1937 | Box 165 \ 2 img103 | |
| Recalibration of a Wraith speedometer. | 12th Jul 1937 | Box 165 \ 2 img104 | |
| The re-calibration of a Wraith speedometer, specifying a change in rev/mile and accuracy. | 13th Jul 1937 | Box 165 \ 2 img105 | |
| Scale calibration data for an A.C. Speedometer, Instrument No. II. | 13th Jul 1937 | Box 165 \ 2 img106 | |
| Scale calibration test report for an A.C. Rev-Counter, instrument number II. | 13th Jul 1937 | Box 165 \ 2 img107 | |
| Calibration figures for the AC type speedometer and rev counter on model 6-B-IV. | 15th Jul 1937 | Box 165 \ 2 img108 | |
| Experimental department report on the bench tests of an AC Bentley Speedometer. | 15th Jul 1937 | Box 165 \ 2 img109 | |
| Test report on an A.C. type speedometer for a Bentley chassis. | 15th Jul 1937 | Box 165 \ 2 img110 | |
| The return of speedometers from chassis 24-G-VI and 25-G-VI for modification. | 4th Aug 1937 | Box 165 \ 2 img111 | |
| Returning Wraith speedometers for recalibration. | 5th Aug 1937 | Box 165 \ 2 img112 | |
| Sending two Wraith III speedometers for recalibration to a new revolutions per mile value. | 10th Aug 1937 | Box 165 \ 2 img113 | |
| Requesting an order for a replacement flexible drive for an AC Speedometer, lost at the coachbuilders. | 7th Sep 1937 | Box 165 \ 2 img114 | |
| Request to remove the speedometer and Rev-counters patch from chassis 6-B-IV for laboratory examination. | 15th Sep 1937 | Box 165 \ 2 img115 | |
| Requesting a bench test for two types of British Jaeger speedometers to compare with standard instruments. | 1st Oct 1937 | Box 165 \ 2 img116 | |
| Memo, which was later cancelled, regarding a standard AT patch for the rev-counter and speedometer for car 6-B-IV. | 5th Oct 1937 | Box 165 \ 2 img117 | |
| Sending a Bentley speedometer for repair to the odometer mechanism. | 11th Oct 1937 | Box 165 \ 2 img118 | |
| Urgent request to remove a speedometer from vehicle 6-B-IV and deliver it to the electrical laboratory. | 11th Oct 1937 | Box 165 \ 2 img119 | |
| Urgent internal memo requesting the return of a speedometer from vehicle 6-B-IV for repair. | 11th Oct 1937 | Box 165 \ 2 img120 | |
| Figures for new Bentley wheel and tyre sizes and requesting the alteration of speedometers on production. | 12th Oct 1937 | Box 165 \ 2 img121 | |
| Cancelling a previous instruction to change over to AT. Instruments on a car. | 12th Oct 1937 | Box 165 \ 2 img122 | |
| Advice note from AC-Sphinx Sparking Plug Co. Ltd. regarding a returned and corrected AC Speedometer. | 13th Oct 1937 | Box 165 \ 2 img123 | |
| Request to order an AC speedometer and rev-counter from AC-Sphinx Sparking Plug Co. Ltd for use on a Bentley. | 13th Oct 1937 | Box 165 \ 2 img124 | |
| Letter from AC-Sphinx apologising for an incorrectly geared speedometer from a Bentley car. | 14th Oct 1937 | Box 165 \ 2 img125 | |
| Letter to the A.C. Sphinx Sparking Plug Co. regarding a faulty speedometer, new instruments, and a rev-counter gadget. | 1st Nov 1937 | Box 165 \ 2 img126 | |
| Letter detailing the investigation and preliminary test results of a British Jaeger Magnetic and a Chrometric speedometer. | 2nd Nov 1937 | Box 165 \ 2 img127 | |
| Request for information on instruments and speedometer drive cables for investigation by the Chassis Electrical Laboratory. | 2nd Nov 1937 | Box 165 \ 2 img128 | |
| Letter from AC-Sphinx Sparking Plug Co. regarding the manufacture of Bentley instruments, discussing dial lighting, a pointer issue, and supply delays for glass. | 3rd Nov 1937 | Box 165 \ 2 img129 | |
| Confirming a Bentley revolution counter from A.T. Speedometer Co. is ready for fitting to a chassis. | 4th Nov 1937 | Box 165 \ 2 img130 | |
| Letter from The A.T. Speedometer Co. Ltd. discussing the performance of Jaeger speed indicators. | 4th Nov 1937 | Box 165 \ 2 img131 | |
| Page 2 of a continuation letter from A.T. Speedometer Co. Ltd. regarding arrangements for tests. | 10th Nov 1937 | Box 165 \ 2 img132 | |
| Fitting a shorter than specified speedometer drive cable due to a supplier error. | 10th Nov 1937 | Box 165 \ 2 img133 | |
| Letter to A.T. Speedometers regarding the return and overhaul of two experimental speed indicators. | 12th Nov 1937 | Box 165 \ 2 img134 | |
| The testing of two cheaper A.T. speedometers and the decision to return them. | 13th Nov 1937 | Box 165 \ 2 img135 | |
| Return and replacement of a Bentley revolution counter. | 15th Nov 1937 | Box 165 \ 2 img136 | |
| Request to arrange the return of an experimental special rev. counter to the A.T. Speedometer Co. | 16th Nov 1937 | Box 165 \ 2 img137 | |
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