Inliners International Forums General Discussion Drive Train 1961 1/2 ton center section question

I have a rearend fron a 1961 chevy 1/2 ton and on the center punkin there is "F1215" I have searched for a decoder but came up blank.

Does anybody have any idea what I have here? I did not remove the center section from the housing yet.

Thanks
Tom

I know that later 60's 1/2 tons were 12 bolt truck rears used up into the late 70's. I'm pretty sure yours is a 12 bolt,the center section should be non drop out unlike the 1960 and earlier rear differentials.Look up 12 bolt truck rear on Google images ,be a 1000 photos.