I just received a set of (guessing they are rather vintage) dies for the 222 Rem Mag made by RCBS in great shape, (Thanks Trapper).

There are 3 dies in the box, one is the seater marked "RCBS 222 R. MG. SEAT 75".
The next is the FL Sizer marked "RCBS 222 R. MG. F.L. 75"
The third is another FL sizer marked "RCBS 222 R. MG. F.L. 67".
Box itself is marked "FL DIE SET .222 REM MAG", Group "D", Part Number "11001".

My question is what is the difference between the FL sizers since one is marked with the number "75" same as the seater and the other is marked "67" ?

What is the reason for the 2 digit numbers on the dies at all?

I am not fluent in RCBS markings as I have mostly been a Lee and Redding kinda guy, but as time goes on I am acquiring more RCBS and Hornady stuff, and this just kinda stumped me. I looked around the RCBS website and did not see anything describing such numberings and the one newer set of RCBS dies I have does not have any such numberings. Was wondering if possibly it was an older way to mark the Small Base dies or something although my 7RM set says "Small Base" right on the die so I dunno.

It's probably something simple and I am just not familiar with the RCBS markings system, so someone feel free to school me. Curiosity is getting the better of me.

Thanks in advance.