Just joined

[Gav]

Hello from London uk.

started collecting m65 jackets recently, have question so joined this forum as undoubtedly there are people on here with lots of knowledge. 
Firstly hello to everyone.

Next the question.

Question is which may be stupid in your eyes but I’m a little confused and still learning   Is referring to the stock numbers on the m65 jackets and why some start 8405 which the four I have in my collection do and some I’ve seen start 8415.

could someone please explain the difference if any.