RCBS Die Question

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.

I thought group D was neck sizer. I guess I was incorrect.

the numbers are year of production

Well that would make sense I guess. Thanks.

I just hadn't seen year of production on any other dies and didn't think about that being a possibility. I'll have to dig out some of the RCBS dies I put back that were from Grandpa's equipment and see if they are marked similarly, just out of curiosity. I put them up since a couple were in calibers I will probably never use (like 219 Zipper Improved and 22 Lovell) but want to hang onto them cuz they were his.

Frank that is correct from what I got from RCBS the 2 numbers are the year of mfg. The Group letter is relative to the popularity and amount produced. Unless my mind is fading again that is what I remember when I asked some where a few years ago.