Looking to find out what an OR code 10 bolt is

Got a rear with the O R code on it. Tried finding a listing of GM codes to see what it's from, and what the ratio is. Anyone know what is, or better yet a GM master list.
Thanks Fred

 

Anyone?

 

Fred, the only place I found it was page 25 of the Steve Dove GS book, 65-67 3.55 posi.

 

Fred,
Is it an A-body rear? Do you have any pictures of the actual code? I’ve had some that were mis-stamped or not stamped correctly,and did not have the correct code. One of my 1970 GS cars has the original rearend that has a code for a 2:93 posi,and I honstely thought that is what is was,UNTIL I opened it up. It was a 3:23 non-posi. I’ve worked on enough of these to tell if they have EVER been worked on or tampered with,and this one was definitely not.

 

Need more info Year, type rear, chassis of rear.