500T frame and engine number

F gives the build year as 1951

3T gives the model code  for  a  500T

The 5 digit number however does not seem to fit a build of that year; more likely a 1948 version.

Frame numbers are usually found on the lug that supports the tank on the left side or on the  headstock.

Jon

The number stamped on the top tube, where it was presumably intended to be hidden once complete is the factory 'shop' number. Have you looked below that, at the front fuel tank lug ?

The "C" prefix to the engine number indicates 1948.

As Richard says is, C prefix denoting 1948,  but the number range is listed as a 1949.
 

The “frame” number looks like a shop number. The location should be on that tank support casting left side. 

 These numbers should actually match for that period.  
Jon

http://classicenglishbikes.com/tech_file/norton.html

Your engine number rang a bell in my brain. I've checked my data and one of my bikes has an engine number 3 before yours.

It's despatch date was 17th October 1951 so, without any unexpected production delays, your despatch date should be within a couple of weeks around this date. Bikes were usually make in small batches.

The frame number, as other members have already documented, should match the engine number.

Bikes made after August are classified as next year's model. So based solely on the engine number it should be correctly identified as a 1952 model.

Look for the frame number near the front left hand petrol tank mount.

The number 21054 belongs to the 1949 model year so the frame number should be D3T 21054 (again assuming no production delays).

You should check out both numbers with the singles dating officer as the Factory Records may explain the differences. There are cases where an owner returns the machine for fitment of a new engine for example.

Factory or bitza?