Tr5t Serial Numbers

Just bought a TR5T Trophy Trail (the US moniker) or Adventurer in the UK. My bike was a US export brought back a few years ago.
It's got matching numbers, beginning PH 19***. According to the Triumph workshop manual, P denotes November and H denotes 1973. However, I also have a certificate from the Triumph Owners Club giving date of manufacture as 15 December 1972, and date of dispatch as 22 January 1973.
The bike would appear to be genuine, the engine number still shows the "Triumph" stamps around it.
Has anyone come across similar anomalies before? Any help much appreciated.

 

Thanks for your reply. So the engine/frame prefix letters indicate a date 11 months ahead of the actual date of manufacture! Well that's logical!

 

Definitely a rider. Not fully original, with B50 tank and a couple of other non-standard parts, but it's all good!