| Description | Date | Identifier | |
| Analysis of speedometer failures for the 25 HP and Phantom II models, detailing noisy operation versus complete failure. | 8th May 1934 | Box 59 \ 2 Scan394 | |
| Letter from A.T. Speedometer Co., Ltd. reporting on the examination of a speedometer. | 31th May 1934 | Box 59 \ 2 Scan395 | |
| Delaying the standardisation of speedometers pending a decision on new internal illumination arrangements. | 1st Jun 1934 | Box 59 \ 2 Scan396 | |
| List of speedometer complaints and investigation findings for 25HP models. | 1st Jun 1934 | Box 59 \ 2 Scan397 | |
| Fault and repair log for instruments on the 25HP model, listing order numbers and resolutions. | 1st Jun 1934 | Box 59 \ 2 Scan398 | |
| List of speedometer faults for the 40/50 HP model, detailing order numbers, specific issues, and resolutions. | 1st Jun 1934 | Box 59 \ 2 Scan399 | |
| Letter to A.T. Speedometer Co. Ltd. regarding the failure of a lightened type speedometer during testing. | 6th Jun 1934 | Box 59 \ 2 Scan400 | |
| Arrangement for the return of a lightened type Bentley speedometer for examination. | 6th Jun 1934 | Box 59 \ 2 Scan401 | |
| Letter from A.T. Speedometer Co., Ltd. regarding the repair of a speedometer's bearing jewel screws. | 7th Jun 1934 | Box 59 \ 2 Scan402 | |
| Letter from a supplier explaining the cause of a broken cog in a trip mileage counter and the implemented solution. | 9th Jun 1934 | Box 59 \ 2 Scan403 | |
| Letter from A.T. Speedometer Co. Ltd. apologising for a design lapse on light-weight instruments. | 9th Jun 1934 | Box 59 \ 2 Scan404 | |
| Outline drawing of a trip assembly for a new lightweight instrument. | 11th Jun 1934 | Box 59 \ 2 Scan405 | |
| Letter from A.T. Speedometer Co. regarding the supply and testing of a lightweight speedometer. | 14th Jun 1934 | Box 59 \ 2 Scan406 | |
| Letter from The A.T. Speedometer Co. Ltd. regarding a returned and examined Rev-Clock. | 21th Jun 1934 | Box 59 \ 2 Scan407 | |
| Letter from a supplier concerning a fault with the clocks in Bentley Rev-Counters and the proposed solution. | 7th Jun 1934 | Box 59 \ 2 Scan408 | |
| Production delays for a lightened speedometer due to issues with larger trip figures and a new illumination method. | 26th Jun 1934 | Box 59 \ 2 Scan409 | |
| Hesitation to standardize a new lightened speedometer due to multiple test failures and the need for a redesign to eliminate magnetic interference. | 27th Jun 1934 | Box 59 \ 2 Scan410 | |
| Magnetic interference issues of the A.T. speedometer compared to other instruments. | 27th Jun 1934 | Box 59 \ 2 Scan411 | |
| Returning a Bentley speedometer for recalibration due to it reading too fast. | 27th Jun 1934 | Box 59 \ 2 Scan412 | |
| Return of an A.T. rev clock for regulation to the A.T. Speedometer Co. | 2nd Jul 1934 | Box 59 \ 2 Scan413 | |
| Letter regarding a faulty Bentley rev-clock being returned for regulation after gaining time. | 2nd Jul 1934 | Box 59 \ 2 Scan414 | |
| Requesting a print showing new dimensions for the instrument panel on the Experimental Bentley 5-B-4. | 3rd Jul 1934 | Box 59 \ 2 Scan415 | |
| Letter from the A.T. Speedometer Co. about an issue with a returned Bentley Rev-Clock. | 6th Jul 1934 | Box 59 \ 2 Scan416 | |
| The blueprint for an instrument board for the Experimental Bentley 5-B-4. | 7th Jul 1934 | Box 59 \ 2 Scan417 | |
| Letter regarding the urgent return of two instruments for calibration and alteration for an E.R. Hall Bentley. | 9th Jul 1934 | Box 59 \ 2 Scan418 | |
| Letter concerning the testing and regulation of a Rev-Clock and Speedometer for Mr. E. R. Hall's Bentley. | 12th Jul 1934 | Box 59 \ 2 Scan419 | |
| Faulty Bentley speedometer where the trip meter cannot be set to zero. | 18th Jul 1934 | Box 59 \ 2 Scan420 | |
| Inspection and repair of a Bentley chassis speedometer. | 20th Jul 1934 | Box 59 \ 2 Scan421 | |
| Letter from The A.T. Speedometer Co. regarding a faulty Bentley Speedometer trip function. | 24th Jul 1934 | Box 59 \ 2 Scan422 | |
| Letter from S. Smith & Sons regarding a visit to discuss an A.T. Speedometer with special screening to eliminate magnetic interference. | 30th Jul 1934 | Box 59 \ 2 Scan423 | |
| Postscript from S. Smith & Sons regarding the testing of new light type A.T. instruments and mileage recorders. | 30th Jul 1934 | Box 59 \ 2 Scan424 | |
| Return of an unsatisfactory speedometer head for chassis No. 85-RY. | 31th Jul 1934 | Box 59 \ 2 Scan425 | |
| Confusion over the correct speedometer calibration for the 20/25 Chassis 1150 Axle. | 31th Jul 1934 | Box 59 \ 2 Scan426 | |
| Letter from France discussing issues with headlamps for continental driving and speedometer calibration. | 1st Aug 1934 | Box 59 \ 2 Scan427 | |
| Letter from The A.T. Speedometer Co., Ltd. discussing the finalisation and requested modifications for a lightweight speedometer and multi-instrument samples. | 3rd Aug 1934 | Box 59 \ 2 Scan428 | |
| Letter from a speedometer company discussing instrument samples and specifications for various car models. | 3rd Aug 1934 | Box 59 \ 2 Scan429 | |
| Continuation letter from A. T. Speedometer Co., Ltd. suggesting an extended arrangement for dial alterations. | 28th Aug 1934 | Box 59 \ 2 Scan430 | |
| Request to return a speedometer for alteration of the 'revs per mile' figure to suit a 12/41 axle. | 28th Aug 1934 | Box 59 \ 2 Scan431 | |
| Letter to A.T. Speedometer Co. Ltd. regarding faults found during testing of a new trip and total mileage recorder. | 5th Sep 1934 | Box 59 \ 2 Scan432 | |
| Letter from S. Smith & Sons discussing a new speedometer design for an instrument panel. | 14th Sep 1934 | Box 59 \ 2 Scan433 | |
| Letter to Messrs. S. Smith & Sons Ltd. confirming a visit to inspect a speedometer and discussing travel arrangements. | 19th Sep 1934 | Box 59 \ 2 Scan434 | |
| Instruction to fit a lightened type A.T. speedometer and rev clock, removed from chassis 4.B.IV, to a Bentley chassis 1.B.IV. | 25th Sep 1934 | Box 59 \ 2 Scan435 | |
| Inquiry regarding a lightened type speedometer for R-R and Bentley chassis. | 27th Sep 1934 | Box 59 \ 2 Scan436 | |
| Delay in standardizing instruments due to a trip counter failure. | 28th Sep 1934 | Box 59 \ 2 Scan437 | |
| Modifications and testing of trip counter instruments for R.R. & Bentley chassis. | 10th Oct 1934 | Box 59 \ 2 Scan438 | |
| Letter from The A.T. Speedometer Co. Ltd. regarding design changes and a timeline for new discs and pinions. | 18th Oct 1934 | Box 59 \ 2 Scan439 | |
| Request to return a lightened type speedometer and rev clock for overhaul and modification. | 18th Oct 1934 | Box 59 \ 2 Scan440 | |
| Letter confirming a telegram regarding an instrument with a non-interfering magnet being sent for trial. | 24th Oct 1934 | Box 59 \ 2 Scan441 | |
| Requesting the completion of the speedometer drive design for a Wraith gearbox to be used in a Bentley. | 24th Oct 1934 | Box 59 \ 2 Scan442 | |
| The alteration of speedometer drive gears for the Spectre chassis. | 5th Nov 1934 | Box 59 \ 2 Scan443 | |
| Speedometer gear ratios and revolutions per mile for the Second Spectre chassis. | 6th Nov 1934 | Box 59 \ 2 Scan444 | |
| Complaint letter to the A.T. Speedometer Co. regarding faulty workmanship on a speedometer from Mr. Fedden's Bentley chassis. | 6th Dec 1934 | Box 59 \ 2 Scan445 | |
| Requesting the repair of a broken A.T. Speedometer total mileage recorder. | 6th Dec 1934 | Box 59 \ 2 Scan446 | |
| Letter from The A.T. Speedometer Co., Ltd. responding to a complaint about a faulty speedometer on a Bentley chassis. | 7th Dec 1934 | Box 59 \ 2 Scan447 | |
| Continuation letter from A. T. Speedometer Co., Ltd. regarding an instrument issue and manufacturing improvements. | 7th Dec 1934 | Box 59 \ 2 Scan448 | |
| Update on the supply of lightened type instruments from the A.T. Company. | 12th Dec 1934 | Box 59 \ 2 Scan449 | |
| Replying to a query about a delay in receiving lightened type instruments sent for modification. | 13th Dec 1934 | Box 59 \ 2 Scan450 | |
| Letter to S. Smith & Sons Ltd. regarding the poor damping of an A.T. speedometer compared to one on a Graham-Paige car. | 19th Dec 1934 | Box 59 \ 2 Scan451 | |
| Letter from S. Smith & Sons discussing speedometer designs and tests. | 21th Dec 1934 | Box 59 \ 2 Scan452 | |
| Sending a Bentley standard A.T. speedometer to the stores for production stock. | 22th Dec 1934 | Box 59 \ 2 Scan453 | |
| Expressing dislike for electric horns due to battery drain and inharmonic sound. | 9th Sep 1910 | Box 59 \ 3 Scan001 | |
| Departmental memo discussing the selection of a suitable road-clearing horn for trials cars. | 22th Mar 1912 | Box 59 \ 3 Scan002 | |
| Continuation page of a departmental memo addressed to Mr. Cowen for consideration and report. | 23th Jan 1912 | Box 59 \ 3 Scan003 | |
| Departmental memo discussing the use of Klaxon and 'Autovox' horns on trials cars. | 11th Apr 1912 | Box 59 \ 3 Scan004 | |
| Departmental memo confirming a 'Bleriot' mechanical horn has been supplied on approval for testing. | 3rd Apr 1913 | Box 59 \ 3 Scan005 | |
| The testing of a Bleriot mechanical horn. | 4th Apr 1913 | Box 59 \ 3 Scan006 | |
| Departmental memo regarding a 'Warningtone' horn supplied for inspection and trial. | 11th Apr 1913 | Box 59 \ 3 Scan007 | |
| Warnington horn supplied for inspection and trial. | 14th Apr 1913 | Box 59 \ 3 Scan008 | |
| Mr. Royce's remarks on an urgency report concerning standard horn and Claxhorn fittings. | 28th Apr 1913 | Box 59 \ 3 Scan009 | |
| Inquiry about the intention to keep or return 'Warningtone' and 'Vibrophone' horns obtained on approval. | 20th May 1913 | Box 59 \ 3 Scan010 | |
| The decision to keep or return Warnington and Vibrophone horns. | 20th May 1913 | Box 59 \ 3 Scan011 | |
| Suitability of Warnington and Vibrophone horns. | 20th May 1913 | Box 59 \ 3 Scan012 | |
| Instruction for Mr Haldenby to return Warnington and Vibrophone horns. | 22th May 1913 | Box 59 \ 3 Scan013 | |
| Request to return Warrington and Vibrophone horns to the makers. | 22th May 1913 | Box 59 \ 3 Scan014 | |
| Criticism of the Warnington Horn and the Vibrophone Horn. | 26th May 1913 | Box 59 \ 3 Scan015 | |
| Return of an Atlas Vibrophone horn to its makers. | 27th May 1913 | Box 59 \ 3 Scan016 | |
| Value and potential issues of a 'Vacuphon' horn. | 29th May 1914 | Box 59 \ 3 Scan017 | |
| Feasibility and potential issues of a 'Vacuphon' Horn. | 5th Jun 1914 | Box 59 \ 3 Scan018 | |
| To Mr. Hives regarding an invoice for a motor horn and a reminder of correct purchasing procedures. | 31th Oct 1919 | Box 59 \ 3 Scan019 | |
| Notification of an order placed for three Lucas Nickel Hand Horns against order 735. | 20th Nov 1919 | Box 59 \ 3 Scan020 | |
| Letter from The Apollo Plug Manufacturing Co. Ltd. regarding their new model horns for the 1920 Motor Show. | 2nd Nov 1920 | Box 59 \ 3 Scan021 | |
| Letter to Apollo Manufacturing Company requesting a trial sample of their No.1, 12-volt Apollo Electric Horn. | 9th Dec 1920 | Box 59 \ 3 Scan022 | |
| Extract from a letter by C.A. Vandervell & Co. Ltd. regarding a new C.A.V. electric horn. | 1st Mar 1921 | Box 59 \ 3 Scan023 | |
| Letter and catalogue from The Benjamin Electric Ltd. for an electric horn. | 26th Oct 1921 | Box 59 \ 3 Scan024 | |
| Letter from The Benjamin Electric Ltd. offering their electric horns for test purposes and potential supply. | 25th Oct 1921 | Box 59 \ 3 Scan025 | |
| Standardization of a 'Boa Constrictor' horn for the Goshawk model and other cars. | 2nd Feb 1922 | Box 59 \ 3 Scan026 | |
| Letter from Clear-Hooters Ltd regarding the supply and testing of a 12-volt Black Clear Hooter. | 9th Feb 1922 | Box 59 \ 3 Scan027 | |
| Suitability and fitting options for a horn on the Goshawk model. | 8th Mar 1922 | Box 59 \ 3 Scan028 | |
| Replacement of the Cobra Horn with the Lucas type 38T horn on works cars due to fitting and water ingress issues. | 9th Mar 1922 | Box 59 \ 3 Scan029 | |
| Urgent memo regarding the fitting of a Boa Constrictor Horn to the Goshawk car. | 10th Mar 1922 | Box 59 \ 3 Scan030 | |
| Requesting the testing of a sample LOTON 2-Note Horn received from Messrs. Brown of Liverpool. | 9th Apr 1923 | Box 59 \ 3 Scan031 | |
| Internal inquiry regarding the availability and fitting of a 'Strombos Horn' for the American market. | 22th Aug 1923 | Box 59 \ 3 Scan032 | |
| Fault with 20 HP & 40/50 HP bulb horns caused by water ingress and a proposed fix. | 28th Jan 1924 | Box 59 \ 3 Scan033 | |
| Follow-up note requesting a reply regarding a 2-note Electric Horn from Brown & Co. Liverpool. | 31th Jan 1924 | Box 59 \ 3 Scan034 | |
| Recommending the purchase of the electric horn from Brown & Co. Ltd. | 2nd Feb 1924 | Box 59 \ 3 Scan035 | |
| Use of exhaust cutouts, proposing they become an optional extra, and also commenting on horns. | 2nd Feb 1924 | Box 59 \ 3 Scan036 | |
| Request for three spare reeds for a 40/50 HP type Boa Constrictor Horn. | 22th Dec 1924 | Box 59 \ 3 Scan037 | |
| Packing note for the dispatch of three reeds for 40/50 model horns. | 29th Dec 1924 | Box 59 \ 3 Scan038 | |
| Request to remove the special Clear-Hoot horn from chassis number 44.PK. | 13th Mar 1925 | Box 59 \ 3 Scan039 | |
| Confirming the dispatch of a 'Clear Hoot Horn' for chassis 44-PK. | 17th Mar 1925 | Box 59 \ 3 Scan040 | |
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