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.