| Description | Date | Identifier | |
| Faulty sample of a Hobbs Motor Car Heat Indicator. | 21th Jun 1922 | Box 33 \ 5 Scan030 | |
| Query comparing the specified characteristics of a generator for an aircraft engine revolution indicator with the Rolls-Royce equivalent. | 14th Aug 1922 | Box 33 \ 5 Scan031 | |
| Cover note for an enclosed leaflet describing the Gallometer by Best & Lloyd. | 28th Nov 1922 | Box 33 \ 5 Scan032 | |
| Informational leaflet explaining the operation and principle of the Gallometer for measuring fuel consumption. | 28th Nov 1922 | Box 33 \ 5 Scan033 | |
| Promotional leaflet for the 'GALLOMETER', a device for measuring a car's fuel consumption. | 29th Nov 1922 | Box 33 \ 5 Scan034 | |
| Hasler Revolution Counter being sent to stores for return to the manufacturer for repair. | 29th Nov 1922 | Box 33 \ 5 Scan035 | |
| Return of a Hasler Revolution Counter for repair. | 15th Feb 1923 | Box 33 \ 5 Scan036 | |
| Letter to the Hasler Telegraph Works requesting the prompt return of a 'Revolutions Counter' sent for repair. | 8th Mar 1923 | Box 33 \ 5 Scan037 | |
| Instruction and feature leaflet for a Hasler revolution and speed indicator tool. | 9th Sep 1922 | Box 33 \ 5 Scan038 | |
| Letter from Hasler Telegraph Works regarding a missing indicator sent for repair. | 9th Mar 1923 | Box 33 \ 5 Scan039 | |
| Quote from Hasler Telegraph Works for the repair and fitting of new parts to an indicator instrument. | 13th Mar 1923 | Box 33 \ 5 Scan040 | |
| Letter authorizing Hasler Telegraph Works to proceed with necessary repairs. | 14th Mar 1923 | Box 33 \ 5 Scan041 | |
| Letter from Hasler Telegraph Works regarding the dispatch of a repaired Speeds Indicator. | 21th Mar 1923 | Box 33 \ 5 Scan042 | |
| Requesting instructions for returning a Hasler revolution counter for repair. | 22th Mar 1923 | Box 33 \ 5 Scan043 | |
| Letter enclosing a quotation for a Cambridge Micro-indicator and accessories. | 16th Apr 1923 | Box 33 \ 5 Scan044 | |
| Quotation from The Cambridge and Paul Instrument Company, Limited for a micro-indicator and various accessories. | 16th Apr 1923 | Box 33 \ 5 Scan045 | |
| Article from 'ENGINEERING' magazine describing the Collins Micro-Indicator for high-speed engines. | 9th Jun 1922 | Box 33 \ 5 Scan046 | |
| Sales letter from German instrument manufacturer OSA Apparate-Gesellschaft promoting their dashboard instruments for motor-cars. | 18th Aug 1923 | Box 33 \ 5 Scan047 | |
| Circular letter from OSA Apparate-Gesellschaft regarding tachometers, clocks, and manometers for motor vehicles. | 18th Aug 1923 | Box 33 \ 5 Scan048 | |
| Promotional letter from OSA Apparate-Gesellschaft M.B.H. for the Optical Indicator Manograf Otto Schulze. | 1st Jan 1921 | Box 33 \ 5 Scan049 | |
| 1921 French catalog for OSA brand speedometers, clocks, and tachometers for automobiles and motorcycles. | 1st Jan 1921 | Box 33 \ 5 Scan050 | |
| Price list for OSA clocks designed for motor-cars and motor-cycles. | 1st Jan 1921 | Box 33 \ 5 Scan051 | |
| Tear-off order form for an OSA Speedometer with Cardan Shaft Drive, including a diagram and vehicle specification questions. | 22th Nov 1923 | Box 33 \ 5 Scan052 | |
| The purchase of a Revolution Counter from The Hasler Telegraph Works. | 22th Nov 1923 | Box 33 \ 5 Scan053 | |
| Return of a Hasler Revolution Counter to its makers for repair. | 24th Nov 1923 | Box 33 \ 5 Scan054 | |
| Letter to Hasler Telegraph Works regarding the repair of a Hasler Revolution Counter. | 24th Nov 1923 | Box 33 \ 5 Scan055 | |
| Instruction to authorise The Hasler Telegraph Works to proceed with estimated repairs. | 1st Dec 1923 | Box 33 \ 5 Scan056 | |
| Letter from Hasler Telegraph Works confirming the dispatch of a repaired Speeds Indicator and enclosing the invoice. | 3rd Dec 1923 | Box 33 \ 5 Scan057 | |
| Despatch of a Hasler Revolution Counter for repair. | 16th Aug 1924 | Box 33 \ 5 Scan058 | |
| List of two Hasler revolution counters with their corresponding serial numbers. | 28th Oct 1924 | Box 33 \ 5 Scan059 | |
| Return of a Hasler revolution counter, No. 5596, to the makers for repair. | 28th Oct 1924 | Box 33 \ 5 Scan060 | |
| The despatch of a Revolution Counter for repair. | 10th Dec 1924 | Box 33 \ 5 Scan061 | |
| Calculations for a Speed Indicator Tester Motor, including flux, frequency, and turns per volt. | 5th Feb 1925 | Box 33 \ 5 Scan062 | |
| Requesting the return of a Hasler Revolution Counter to its makers for repair. | 9th Jun 1925 | Box 33 \ 5 Scan063 | |
| Return of a Revolution Counter for repair or replacement allowance. | 1st Jun 1925 | Box 33 \ 5 Scan064 | |
| Official order for repairs to a Hasler Revolution Counter. | 1st Jul 1925 | Box 33 \ 5 Scan065 | |
| Despatch of a Revolution Counter for repair. | 27th Aug 1925 | Box 33 \ 5 Scan066 | |
| Electrical specifications for a Weston Revs Per Minute Indicator, Model 267. | 13th Oct 1925 | Box 33 \ 5 Scan067 | |
| Test report for a Weston R.P.M. Indicator, instrument model 269. | 22th Oct 1925 | Box 33 \ 5 Scan068 | |
| Request to order one Hasler Speed Indicator for the Experimental Department due to shortages caused by frequent repairs. | 25th Nov 1925 | Box 33 \ 5 Scan069 | |
| Requesting the return of a Hasler Revolution Counter to the makers for repair. | 20th Nov 1925 | Box 33 \ 5 Scan070 | |
| Letter from the Royal Aircraft Establishment regarding the loan of an Air Speed Indicator for experimental work. | 5th Dec 1925 | Box 33 \ 5 Scan071 | |
| Loan of an Air Speed Indicator and a Pitot Head from R.A.E. Farnborough for experimental testing. | 9th Dec 1925 | Box 33 \ 5 Scan072 | |
| Receipt and return of an air speed indicator and pitot head to R.A.E., South Farnborough. | 29th Dec 1925 | Box 33 \ 5 Scan073 | |
| Technical drawing for a Driven Wheel for a Revolution Counter. | 1st Dec 1926 | Box 33 \ 5 Scan074 | |
| Technical drawing for a Driving Pinion, revision Counter. | 12th Jan 1926 | Box 33 \ 5 Scan075 | |
| Technical drawing for an Intermediate Pinion for a Reverse Counter. | 12th Nov 1926 | Box 33 \ 5 Scan076 | |
| Technical drawing of an Intermediate Wheel for a Revolution Counter. | 12th Jan 1926 | Box 33 \ 5 Scan077 | |
| Trials log for a speed indicator tester. | 18th Mar 1926 | Box 33 \ 5 Scan078 | |
| Data log sheet recording the results from trials of a speed indicator tester. | 18th Mar 1926 | Box 33 \ 5 Scan079 | |
| Log of trials for a speed indicator tester. | 25th Feb 1925 | Box 33 \ 5 Scan080 | |
| Table recording the results from trials of a speed indicator tester. | 17th May 1926 | Box 33 \ 5 Scan081 | |
| Data log of trials for a speed indicator tester, recording frequency and percentage speed variations over time. | 17th May 1926 | Box 33 \ 5 Scan082 | |
| Log of trials for a speed indicator tester, showing results from April 1926. | 17th May 1926 | Box 33 \ 5 Scan083 | |
| Log sheet detailing the results from trials of a speed indicator tester. | 17th May 1926 | Box 33 \ 5 Scan084 | |
| Log sheet detailing the results of trials conducted on a speed indicator tester. | 17th May 1928 | Box 33 \ 5 Scan085 | |
| Returning a Hasler Revolution Counter to the makers for repair. | 18th Jan 1926 | Box 33 \ 5 Scan086 | |
| Faulty Hasler revolution counter being sent for alteration. | 18th Mar 1926 | Box 33 \ 5 Scan087 | |
| Hasler Revolution Counter being sent to the stores for repair by the makers. | 27th Apr 1926 | Box 33 \ 5 Scan088 | |
| Requesting the repair of a Hasler Revolution Counter by a clock maker. | 17th Nov 1926 | Box 33 \ 5 Scan089 | |
| Returning a faulty Hasler revolution counter due to a sticking needle. | 6th Dec 1926 | Box 33 \ 5 Scan090 | |
| Report concerning a broken spring on a Revolution Circumferential and Cutting Speeds Indicator, which will be repaired free of charge. | 10th Dec 1926 | Box 33 \ 5 Scan091 | |
| Instruction to send a Hasler Revolution Counter for repair. | 31th Dec 1926 | Box 33 \ 5 Scan092 | |
| Request to return a faulty Hasler revolution counter for re-adjustment and repair. | 14th May 1927 | Box 33 \ 5 Scan093 | |
| Instructing Stores to despatch a faulty Hasler revolution counter for repair. | 17th May 1927 | Box 33 \ 5 Scan094 | |
| Requesting a Hasler Rev. Counter No. 5596 be returned to its makers for repair. | 27th Jun 1927 | Box 33 \ 5 Scan095 | |
| Improved electrical indicator valve, its use, maintenance, and supply of parts. | 17th Jan 1928 | Box 33 \ 5 Scan096 | |
| Blueprint for an improved electrical indicator valve with component details and dimensions. | 17th Jan 1928 | Box 33 \ 5 Scan097 | |
| Instruction to send a Hasler Revolution Counter for repair and return. | 27th Jun 1928 | Box 33 \ 5 Scan098 | |
| Electrical testing specifications and calculations for a speed indicator tester. | 14th Aug 1928 | Box 33 \ 5 Scan099 | |
| Optimal position of a sparking plug in an engine cylinder. | 18th Jul 1916 | Box 33 \ 5 Scan100 | |
| The testing of different sparking plug positions on the 'Hawk' engine. | 27th Jun 1916 | Box 33 \ 5 Scan101 | |
| Note on observing a pre-igniting plug inside a cylinder. | 9th Sep 1916 | Box 33 \ 5 Scan102 | |
| Spark plug overheating, detailing Mr. Royce's suggestion to use water-cooled copper pipes. | 9th Sep 1916 | Box 33 \ 5 Scan103 | |
| Trial and development of a new 6-volt coil compared to the standard 4-volt version. | 31th Oct 1913 | Box 34 \ 1 Scan001 | |
| Query regarding the winding particulars for a 6-volt ignition coil and the number of plates in the condenser. | 24th Mar 1914 | Box 34 \ 1 Scan002 | |
| The necessity of a condenser folding machine for the standardisation of 6-volt coils. | 21th Apr 1914 | Box 34 \ 1 Scan003 | |
| Confirming a conversation about purchasing a condenser folding machine instead of building one, to aid in standardising the 6 volt coil. | 28th May 1914 | Box 34 \ 1 Scan004 | |
| Two designs for a modified single spark coil to produce a single spark instead of a series. | 28th May 1914 | Box 34 \ 1 Scan005 | |
| Providing specifications for a standard chassis coil in response to a query. | 1st Sep 1915 | Box 34 \ 1 Scan006 | |
| Modifications to the battery ignition system for cars equipped with a self-starter. | 10th Jul 1917 | Box 34 \ 1 Scan007 | |
| Positioning and capacity of ignition condensers and the future adoption of electric starters. | 10th Jul 1917 | Box 34 \ 1 Scan008 | |
| The cost and performance benefits of synchronised battery and magneto ignitions over trembler ignitions. | 10th Jul 1917 | Box 34 \ 1 Scan009 | |
| Extract discussing the placement and use of condensers in trembler ignition systems to reduce the burning of platinum points. | 14th Aug 1919 | Box 34 \ 1 Scan010 | |
| From 'R.' to 'Mr. Ellis' with instructions for converting and testing a battery ignition system. | 27th Aug 1917 | Box 34 \ 1 Scan011 | |
| Conversion of a battery ignition system to a non-trembler type for engine 7-CA. | 27th Aug 1917 | Box 34 \ 1 Scan012 | |
| Letter to Commander Bristow regarding the development and improvement of a battery ignition system for aero engines. | 5th Sep 1917 | Box 34 \ 1 Scan013 | |
| Calculation of the capacity of a condenser. | 28th Dec 1917 | Box 34 \ 1 Scan014 | |
| The calculation of inductance of a coil. | 28th Dec 1917 | Box 34 \ 1 Scan015 | |
| Requesting a modified trembler coil for a battery ignition system, including a hand-drawn diagram. | 12th Mar 1918 | Box 34 \ 1 Scan016 | |
| Specifications and volume requirements for a battery ignition condenser for a 12-volt coil. | 20th Apr 1918 | Box 34 \ 1 Scan017 | |
| Suitability and testing of a 12-volt battery ignition system. | 20th Apr 1918 | Box 34 \ 1 Scan018 | |
| Table of approximate capacitance values in microfarads for various experimental condensers. | 5th Jul 1918 | Box 34 \ 1 Scan019 | |
| Condenser capacity issues related to battery ignition systems. | 5th Jun 1918 | Box 34 \ 1 Scan020 | |
| Investigating disappointing test results on platinum points due to an under-capacity condenser for the battery ignition. | 18th Jun 1918 | Box 34 \ 1 Scan021 | |
| Condenser capacity tests to quench sparks on platinum points and plans for future long-run tests. | 18th Jun 1918 | Box 34 \ 1 Scan022 | |
| Modifying a pocket voltmeter to improve the measurement of condenser capacities. | 2nd Jul 1918 | Box 34 \ 1 Scan023 | |
| Report discussing the fitment of Truffault shock absorbers, starter motors, and battery ignition systems for the 7-CA chassis model. | 5th Jan 1919 | Box 34 \ 1 Scan024 | |
| Ignition gear modifications, condensers, and issues with trembler coils. | 26th Apr 1917 | Box 34 \ 1 Scan025 | |
| Continued note regarding modifications to coils and condensers for existing cars. | 25th Apr 1917 | Box 34 \ 1 Scan026 | |
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