Looks like an M-22 assembled August 31, 1968. One easy way to tell is the input shaft on an M-22 will not have any grooves. One groove would be M-21 and two grooves M-20. This identification method works so long as the input shaft is original to the trans, but pulling side cover is always best.

I've never seen a POP that has the letter of the trans stamped regardless of year or build date of the trans. Oct. 1968 is when the A, B & C were stamped as part of the trans assembly date with "C" meaning M-22 which is why the ebay trans is missing the letter as it was assembled Aug. 31st of 1968. .

The transmission in the link has an assembly date of 9M31

October 68 is when the codes started to get used based on what i have here.....all the P dated P9P xxx cases didnt have codes [september] I have mixed R or october dates S and T [Nov and dec ] all have codes ...

http://www.camaros.org/trans.shtml#4speed
To distinguish between Muncie types, if the Muncie was built after 21-Oct-1968, the transmission code contains one of three letters at the end of the build code...

Looks nice and correct to me.

I can't Thank everybody enough for there input. You guys are the Best !!! ROB

Just so I understand better. The assembly date stamped on it being 9M31. Was this transmission assembled August 31 1969? or 1968? sorry guys I'm just a bit confused and want to understand. Thanks ROB

Trans
 

OCTOBER 21 1968 muncie started the A B C

If it were assembled anytime during calendar year 1969 it would have an A B or C suffix as stated. Always a good idea to check casting dates on the case and tail housing and make sure they precede the assembly date by weeks, not years.

Tranny was built August 31, 1968.

A minor detail, but it has the '70 up style magnetic plugs. Still doesn't prove that case started out as an M22. Anyone can tap the lower boss.

- Warren