Does anyone know how to read the date codes on a "G" y-block head? Also there was a cut off date between the "G" unposted and the "G" posted. I think it was like anything after March 1957 was posted. Anything before March 1957 and including March was unposted.

 

I don't have a quick answer, but I'll check my heads to see which have what.

 

all heads were posted after may i 57.the code reads like this.my heads have 7 4 b on them.the 7 is 57 the 4 is april the letter is for the day.my heads are not posted as you can tell.