| Description | Date | Identifier | |
| Technical memorandum discussing pre-ignition issues caused by Champion ignition plugs. | 9th Sep 1921 | Box 33 \ 3 Scan154 | |
| Selection and performance of spark plugs in various engines. | 9th Sep 1921 | Box 33 \ 3 Scan155 | |
| Follow-up on the trial of French-made sparking plugs offered by a customer for chassis 79-TW. | 9th Sep 1921 | Box 33 \ 3 Scan156 | |
| Requesting an update on the testing of a 'Silca' plug. | 9th Sep 1921 | Box 33 \ 3 Scan157 | |
| Cover of a document titled 'Spark Plug Logic', featuring an illustration of a spark plug. | 9th Sep 1921 | Box 33 \ 3 Scan158 | |
| The stagnation in spark plug design and the problems with various insulating materials. | 13th Sep 1921 | Box 33 \ 3 Scan159 | |
| Follow-up memo from CJ to the Experimental Dept. regarding the testing of a plug. | 13th Sep 1921 | Box 33 \ 3 Scan160 | |
| Test report on a 'Silca' sparking plug. | 9th Sep 1921 | Box 33 \ 3 Scan161 | |
| Testing of a spark plug and proposing design improvements. | 9th Sep 1921 | Box 33 \ 3 Scan162 | |
| Letter from George Roberts following up on sparking plugs sent for testing and offering patent rights. | 16th Sep 1921 | Box 33 \ 3 Scan163 | |
| Request to return a tested sparking plug to Captain Withers. | 17th Sep 1921 | Box 33 \ 3 Scan164 | |
| Arranging the return of a 'Silec' Plug to Captain Withers. | 17th Sep 1921 | Box 33 \ 3 Scan165 | |
| Letter regarding the testing of a 'Silca' spark plug and a request for its return. | 16th Sep 1921 | Box 33 \ 3 Scan166 | |
| Instructing the stores to despatch a 'Silca' sparking plug for testing. | 19th Sep 1921 | Box 33 \ 3 Scan167 | |
| Letter regarding pre-ignition issues with ignition plugs and the successful testing of new Champion plugs. | 20th Sep 1921 | Box 33 \ 3 Scan168 | |
| Sales letter from The Anger Manufacturing & Supply Co Ltd regarding their 'AMASCO' Sparking Plugs. | 20th Sep 1921 | Box 33 \ 3 Scan169 | |
| Page two of a letter from The Anger Manufacturing & Supply Co. Ltd. proposing a trial order for 'AMASCO' sparking plugs. | 20th Sep 1921 | Box 33 \ 3 Scan170 | |
| Advertisement for 'The Anger Amasco Plug', an all-British-made sparking plug. | 22th Sep 1921 | Box 33 \ 3 Scan171 | |
| Letter responding to a query about a non-receipt of spark plugs and requesting dispatch details. | 22th Sep 1921 | Box 33 \ 3 Scan172 | |
| Letter from George Roberts of Peek, Frean & Co. Ltd. confirming a recent inquiry about 'Prima' sparking plugs. | 22th Sep 1921 | Box 33 \ 3 Scan173 | |
| Letter from George Roberts concerning a parcel of Sparking Plugs that may have been misplaced upon arrival. | 23th Sep 1921 | Box 33 \ 3 Scan174 | |
| Letter from George Roberts sending 'Prima' sparking plugs for testing and offering the UK manufacturing and sales rights. | 12th Jul 1921 | Box 33 \ 3 Scan175 | |
| Letter regarding a lost parcel of plugs sent to the Experimental Dept, requesting a new sample for a preliminary report. | 24th Sep 1921 | Box 33 \ 3 Scan176 | |
| Request to search for a customer's misplaced spark plugs sent for experimentation. | 26th Sep 1921 | Box 33 \ 3 Scan177 | |
| Letter from Philip Challis regarding a report on the design features of the Silca Sparking-Plug. | 25th Sep 1921 | Box 33 \ 3 Scan178 | |
| Letter from George Roberts regarding a missing correspondence and offering to send a new series of 12 plugs for trial. | 26th Sep 1921 | Box 33 \ 3 Scan179 | |
| From 'R' discussing the testing of Spinx spark plugs as a potential alternative to unreliable Mercury plugs. | 10th Oct 1921 | Box 33 \ 3 Scan180 | |
| Follow-up communication awaiting a reply regarding plugs sent by Mr. G. Roberts for chassis 79-TW. | 4th Oct 1921 | Box 33 \ 3 Scan181 | |
| Correspondence regarding the misplacement of sparking plugs sent by G. Roberts Esq. for testing. | 10th Oct 1921 | Box 33 \ 3 Scan182 | |
| Letter from George Roberts sending 'Prima' spark plugs for testing, noting a potential thread incompatibility. | 13th Oct 1921 | Box 33 \ 3 Scan183 | |
| Letter acknowledging the receipt of 7 Prima Sparking Plugs for a future report. | 15th Oct 1921 | Box 33 \ 3 Scan184 | |
| Letter regarding the submission of two sets of 'Prima' sparking plugs for testing. | 29th Oct 1921 | Box 33 \ 3 Scan185 | |
| Postcard addressed to the Experimental Department in Derby. | 29th Oct 1921 | Box 33 \ 3 Scan186 | |
| Second set of plugs for Chassis 79-TW. | 2nd Nov 1921 | Box 33 \ 3 Scan187 | |
| Opportunity to acquire manufacturing rights for special plugs from a French inventor. | 31th Oct 1921 | Box 33 \ 3 Scan188 | |
| Letter from AC Sparking Plug Co. Ltd. confirming a quotation and announcing a new English-made plug. | 31th Oct 1921 | Box 33 \ 3 Scan189 | |
| Letter from George Roberts confirming the despatch of six Prima Sparking Plugs for testing. | 8th Nov 1921 | Box 33 \ 3 Scan190 | |
| Follow-up note regarding the performance of a set of Prima Sparking Plugs, attached to the original letter. | 23th Nov 1921 | Box 33 \ 3 Scan191 | |
| Chasing a response for Mr. George Roberts regarding plugs and English rights negotiation for chassis 79-TW. | 17th Nov 1921 | Box 33 \ 3 Scan192 | |
| Pamphlet on sparking plugs from Barracloughs (Engineers) Ltd. | 23th Nov 1921 | Box 33 \ 3 Scan193 | |
| Product page for the 'Patent Model M.W' and 'Bradford Patent Plug', showing the complete assembly and its individual parts. | 23th Nov 1921 | Box 33 \ 3 Scan194 | |
| Guarantee and information leaflet for 'The Bradford' patent plugs. | 26th Nov 1921 | Box 33 \ 3 Scan195 | |
| Letter regarding a delay in testing Prima Sparking Plugs. | 26th Nov 1921 | Box 33 \ 3 Scan196 | |
| Technical evaluation and test report on the 'PRIMA' sparking plug. | 26th Nov 1921 | Box 33 \ 3 Scan197 | |
| Test report conclusion on Prima spark plugs, finding them inferior and not recommended for use. | 28th Nov 1921 | Box 33 \ 3 Scan198 | |
| Letter of acknowledgement for a report regarding unsatisfactory Prima plugs. | 28th Nov 1921 | Box 33 \ 3 Scan199 | |
| Extract from a report detailing a visit to West Wittering regarding spark plug testing for the Goshawk engine. | 30th Dec 1921 | Box 33 \ 3 Scan200 | |
| Requesting attendance at a conference to agree on a policy for ordering sparking plugs. | 27th Jan 1922 | Box 33 \ 3 Scan201 | |
| Letter from C. G. Mason offering a trial set of a French device, 'L'Eclateur Cure', for testing on Aero and car engines. | 3rd Feb 1922 | Box 33 \ 3 Scan202 | |
| Product information and fitting instructions for the 'L'Eclateur Cure' spark plug device. | 23th Feb 1922 | Box 33 \ 3 Scan203 | |
| Letter from C. Meier-Mattes & Co offering Deltavis Sparking Plugs for testing. | 23th Feb 1922 | Box 33 \ 3 Scan204 | |
| Letter from C. Meier-Mattes & Co regarding Deltavis sparking plugs and other precision parts. | 7th Mar 1922 | Box 33 \ 3 Scan205 | |
| Sales letter from Pickard, Dobson & Co Ltd offering a trial set of their 'Platomac' Sparking Plugs. | 23th Mar 1922 | Box 33 \ 3 Scan206 | |
| Instructional leaflet and advertisement for Platomaс spark plugs, detailing gap settings and showing a parts diagram. | 23th Mar 1922 | Box 33 \ 3 Scan207 | |
| Directions for adjusting the gap on a spark plug using a spanner with a built-in feeler gauge. | 23th Mar 1922 | Box 33 \ 3 Scan208 | |
| Advertisement for the Platomac detachable and adjustable sparking plug. | 27th Apr 1921 | Box 33 \ 3 Scan209 | |
| Review of various automotive accessories including a non-fouling spark plug, a spring gaiter, and one-man hood fittings. | 27th Apr 1921 | Box 33 \ 3 Scan210 | |
| Request to arrange testing for eight Type D3 Mica Plugs sent in by the Igna Engineering Co. Ltd. | 25th Apr 1922 | Box 33 \ 3 Scan211 | |
| Letter from Deltavis Co's agent following up on six type Z2 sparking plugs sent for testing. | 27th Apr 1922 | Box 33 \ 3 Scan212 | |
| Internal request to purchase a Westinghouse Neon Gas Spark Plug Tester for the Experimental Department. | 23th Jun 1922 | Box 33 \ 3 Scan213 | |
| Instructions and report on the testing of Del'tavis 215 type plugs. | 4th Jul 1922 | Box 33 \ 3 Scan214 | |
| Forwarding a letter and a Sparking Plug Remover from the Runbaken Magneto Co. Ltd. | 19th Jul 1922 | Box 33 \ 3 Scan215 | |
| Sales letter from The Runbaken Magneto Co Ltd. proposing an accessory for vehicles. | 13th Jul 1922 | Box 33 \ 3 Scan216 | |
| Promotional leaflet for Swiss-made Deltavis spark plugs, valves, whistles, and precision screw parts. | 13th Jul 1922 | Box 33 \ 3 Scan217 | |
| Advertisement leaflet for turned precision parts and high-class screwed ware, detailing types, prices, and quality benefits. | 7th Sep 1922 | Box 33 \ 3 Scan218 | |
| Testing of K.L.G. sparking plugs and the decision to temporarily use Lodge plugs due to potential overoiling issues. | 7th Sep 1922 | Box 33 \ 3 Scan219 | |
| Performance and selection of ignition plugs for the 40/50 and Goshawk models. | 26th Sep 1922 | Box 33 \ 3 Scan220 | |
| Suitability and performance of different spark plugs (K.L.G. and Lodge C.9) for the 40/50 car. | 26th Sep 1922 | Box 33 \ 3 Scan221 | |
| Sending 'M' and 'D' type Metric Plugs from the Forward Sparking Plug Co. for testing. | 29th Sep 1922 | Box 33 \ 3 Scan222 | |
| Letter from A. Picard offering a free set of JAM spark plugs for testing. | 5th Oct 1922 | Box 33 \ 3 Scan223 | |
| Translated testimonial letter regarding the satisfactory performance of J.A.M. plugs. | 9th Nov 1921 | Box 33 \ 3 Scan224 | |
| Testimonial letter from driver Rougier regarding the performance of JAM spark plugs. | 6th Jun 1922 | Box 33 \ 3 Scan225 | |
| Translated testimonial from a customer regarding the performance of plugs after winning a race. | 7th Jun 1922 | Box 33 \ 3 Scan226 | |
| Translated testimonial letter regarding the performance of spark plugs during a Grand Prix event. | 24th Jul 1922 | Box 33 \ 3 Scan227 | |
| Translated testimonial from Etablissements Bablot regarding satisfaction with plugs used in the Boulogne races. | 5th Aug 1922 | Box 33 \ 3 Scan228 | |
| Translated testimonial regarding the standard adoption of J.A.M. plugs Nos 1 and 2 for Hispano Suiza engines. | 29th Dec 1921 | Box 33 \ 3 Scan229 | |
| From GWH to Mr. Hives detailing the results of testing M type and D type forward sparking plugs. | 12th Oct 1922 | Box 33 \ 3 Scan230 | |
| Test report on Block Sparking Plugs type 12/20, noting pre-ignition issues and power loss. | 23th Nov 1922 | Box 33 \ 3 Scan231 | |
| Promotional letter from W. Courte Elektro-Industrie regarding their 'Wico-Eko' three-pole spark plug. | 6th Dec 1922 | Box 33 \ 3 Scan232 | |
| Sales proposal for 'Wico-Mko' Spark-Plugs and a 'Wico' Spark-Plug-Contact. | 6th Dec 1922 | Box 33 \ 3 Scan233 | |
| Advertisement leaflet for an EKO spark plug with 3 electrodes. | 6th Dec 1922 | Box 33 \ 3 Scan234 | |
| Multilingual promotional leaflet for the 'Wico' electrical immersion heater. | 6th Nov 1922 | Box 33 \ 3 Scan235 | |
| Letter from Dowden & Company regarding a client's positive feedback on a Petrol Indicator and 'Block' plugs, which are being sent for testing. | 6th Nov 1922 | Box 33 \ 3 Scan236 | |
| Follow-up letter from Dowden & Company regarding Petrol Indicator and 'Block' plugs sent for testing. | 20th Dec 1922 | Box 33 \ 3 Scan237 | |
| Burnt valves, pre-ignition causes related to spark plugs, and engine performance observations. | 29th Dec 1922 | Box 33 \ 3 Scan238 | |
| The practice of pinning piston rings and its effect on gas-tightness, referencing the 40/50 and Hawk engines. | 6th Jan 1923 | Box 33 \ 3 Scan239 | |
| Letter to Messrs. Dowden & Co. rejecting their Block sparking plugs and petrol level indicator after testing. | 6th Jan 1923 | Box 33 \ 3 Scan240 | |
| Despatch of a Petrol Level Indicator and sparking plugs to Messrs. Dowden for testing and examination. | 6th Jan 1923 | Box 33 \ 3 Scan241 | |
| Letter from Dowden & Co. regarding the receipt of a parcel containing a petrol indicator and sparking plugs. | 10th Jan 1923 | Box 33 \ 3 Scan242 | |
| Ignition plug and switching arrangements for the 40/50 & Goshawk models. | 1st Jan 1923 | Box 33 \ 3 Scan243 | |
| Forwarding particulars for Block plugs and Level Indicators supplied by Messrs. Dowden of London. | 18th Jan 1923 | Box 33 \ 3 Scan244 | |
| Standardisation of the C.56 Lodge ignition plug for 40/50 & Goshawk models, based on a conversation with Mr. Royce. | 23th Jan 1923 | Box 33 \ 3 Scan245 | |
| Request for a suitable cheap spark plug for engine gear quietening tests due to over-oiling issues. | 16th Jul 1924 | Box 33 \ 3 Scan246 | |
| Two special sparking plugs received from Paris for examination and expressing doubts about their utility. | 16th Jul 1924 | Box 33 \ 3 Scan247 | |
| Trouble with sparking plugs on the engine gear quietening stand due to over-oiling, requesting a cheap alternative. | 16th Jul 1924 | Box 33 \ 3 Scan248 | |
| Letter regarding a set of eight Deltavis Z.II sparking plugs sent for testing and evaluation. | 28th Aug 1924 | Box 33 \ 3 Scan249 | |
| Query regarding issues with K.L.G. and Lodge sparking plugs during engine testing and a request for a recommendation for a cheap porcelain alternative. | 13th Nov 1924 | Box 33 \ 3 Scan250 | |
| Recommendation to obtain Champion Sparking Plugs for 20 HP & 40/50 HP chassis testing due to their resistance to sooting. | 19th Nov 1924 | Box 33 \ 3 Scan251 | |
| Special short sparking plugs for testing that are no longer required by R.A.F. Stores. | 28th May 1937 | Box 33 \ 3 Scan252 | |
| Letter forwarding an enquiry about special sparking plugs to the Derby Works for consideration. | 22th Jul 1927 | Box 33 \ 3 Scan253 | |
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