Interesting observation with /306\ guns

[running-man]

So I was looking through some /306\s, categorizing certain things when I noticed something interesting:

13th year:


14th year:


15th year:


16th year:


17th year:


18th year:


Then it stops (maybe we just don't have the 19's through 22's yet) and starts again at 23rd year:

Well that's a different looking stamp.  This 3 is totally different than the stylized "Sigma" style 3 from the previous stamps.  The 0 reaches way up too and has a sharp point on top.

WTH?  Maybe it's a fluke?  Nope:


How'd we miss that one? 

It looks like the /306\ factory most certainly has two different stamps.  It'll be interesting to see when that transition actually occurred and if there were ever any recurrences of the early style stamp.