Tilley X246A - Early and Later

I have labelled some time ago a few of my Tilley X246A as early and later but have now forgotten what the issue was. Perhaps an age thing, (mine)! Can anyone recall? I am certain it was not the hood colour nor the straight legged X246A and I don't think it was the rim height either.

In any case I am interested in: the height difference in one of mine. All of mine have a short rim except for one from 1961.



1961 X246A with a 15 mm rim




All of my other X246A rims look like this:


1963 X246A with 10 mm overall rim height (and all my other X246A are the same as this.)

Lastly, I measure the overall height difference between the 1961 and the others at:

9 mm height difference between my 1961 and all other X246A

Any thoughts please?

PS The blue colour was just my painting of the 1961 lantern.

Thanks

 

I should add, as my post is not clear, that the 1961 lantern is 9 mm taller than all the rest.