The chassis number for these model its composed of an initial fixed letter which is B, followed by a number that can go from 1 to 501 and finally two letters of which the first one determines the series of the model.

Depending on the first letter of the last two letters of your chassis number you can determine what series your car is and look up any modifications done through the range

choose your series

Release dates Car model Chassis number Modification Modification introduced at
 Jun. 52 to Apr. 53  R-Type (R)

 B2RT to B120RT

 Revised luggage boot, automatic SU carburetters, revised attitude rear springs, revised rear shock damper linkage, two speed windscreen wiper, pop-out cigar lighter, separately housed main fuse, caster angle wedges  B2RT 
 Sep. 52 to Apr. 53    B1RS to B121RS  Corrugated bottom water hose connection  B68RT 
 Sep. 52 to May 53  R-Type (R)  B2SR to B500SR  Taper roller bearings on rear axle pinion (except 12/41 axle)  B380SR 
 Jan. 53 to May 53    B1SP to B501SP  Front shock dampers  B61SP 
       Parco lubrized tappets B425SP 
       Taper roller bearings on rear axle pinion 12/41 axle B433SP 
 Apr. 53 to Sep. 53  R-Type (R)  B1TO to B401TO  6.75 compression ratio cylinder head  B93TO 
 Jun. 53 to Dec. 53    B2TN to B600TN   Deletion of non-opposed springs in side steering tube  B313TO 
       All welded frames B349TO 
       Metal facia, cable operated hot and cold, de-mister and underseat heater B2TN 
       Hard clay gasket B373TN 
       Deletion of reduced friction modification on steering connections B390TN 
       Revised throttle controls for synchromesh gearbox B436TN 
 Oct. 53 to Dec. 53  R-Type (R)  B1UL to B251UL  Aluminium flywheel housing  B35UL 
 Nov. 53 to May 54    B2UM to B250UM   Improved type underseat seat tool tray  B66UM 
       Introduction of B-VI type gearbox tie rod B212UM 
 Jan. 54 to May 54  R-Type (R)  B2WH to B300WH  Flywheel inertia ring on cars with auto gearbox B236WH 
 Mar. 54 to Jun. 54    B1WG to B301WG  Dynamo type mounting strap onstarter motor B270WH 
       Thicker 3rd motion shaft thrust washer B89WG 
       Compensator pipe between front and rear servo B183WG 
 May 54 to Jul. 54  R-Type (R)  B2XF to B140XF  Strengthened jaws on front brake operating links B60XF 
 Jun. 54 to Oct. 54  R-Type (R)  B1YA to B331YA  12/41 rear axle (all cars) B1YA 
 Aug. 54 to Nov. 54    B2YD to B330YD  Elimination of chromium-plated servo pressure plate B123YD 
       Long stroke starter pinion B138YD 
       Flexibox seal on water pump  B246YD 
       Bentley continental type de-misting B246YD 
 Oct. 54 to Jan. 55  R-Type (R)  B1ZX to B251ZX  Improved cold starting device B1ZX 
 Dec. 54 to Feb. 55    B2ZY to B250ZY  2nd speed start B73ZX 
       Ferodo washers and drain slots in crankshaft vibration damper B212ZY