Engine and Frame Serial Numbers

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This document currently will help you identify from 1923 to 1975 Norton Models. Pre-war Models were manufacted from 1923 to 1939. Pre-war Models are identified by their Engine Serial numbers. These numbers can be found in Table 4.

Post-war models are denoted from year 1945 on. Post-war Serial Numbers consist of three parts. First a Model Number (Table 2), second a letter code (Table 3), and last a unique number (Table 1). Serial Numbers are found on the Frame and Engine.

The Serial Numbers on the Frame and Engine from 1945 to 1974 should match. The serial numbers from 1960 to 1945 should include a year letter code.

Engine Numbers:

The Engine Numbers are found on the front of the crankcase or on the left-hand crankcase just below the cylinder. The engine number may include the engine dimensions, especially on the singles with the 79X100 mm bore and stroke.

Frame Numbers:

Feather Bed Frames: The serial numbers are located on the primary case side, rear frame gasset (below to the rear swing arm bolt). The Model code is written horizontal with the year letter (if one is present) and the unique number is written vertically.

Commando Frames: The serial numbers on the Commando Frames are numbered on a plate rivited to the headstock.

Small Twins (ie Jubilee):The frame numbers are stamped on the right-hand frame lug which carried the rear fork up to 1963. From then on, it was on the pillion footrest bracket.

Other Frames: The serial numbers are on the headstock.

When trying to date a engine/frame, the year code letter is the most useful up to 1960. The serial numbers have been known to have some overlap from one model year, or calender year, to the next. There are some exceptions to this. The unique numbers written in Table 1 below indicte year end values.

Notes For Translating Model Letters:
Suffix D indicates de luxe twin
Suffix SS indicates Sports Special Twins
Suffix Q indicates quieting ramp cams (some 1947 singles)