Purchased this car new at Gardner Oldsmobile, Sept 69, Has 12 bolt Chevy, need help decoding. Left side of housing 3959028. Right side of housing
(CM2 D N) picture included that shows a small square with a arrow below pointing to left of box between the D and N. Bottom of housing 889C. Axle code not readable. Will be pulling cover off this coming weekend to refresh. Thank you for any comments. Mark

 

I believe the CM2 and D N are simply casting molds at CFD (Central Foundry Dvision) of GM and don't have any significance to the overall axle. If the axle code is not readable you could check your original bill of sale since you were the original purchaser, or since it's an almost 50 year old car, pull the cover and change the fluid (stinky job BTW) and check the stamping on the ring gear. That will tell you proof positive what it is.

Here's some information from the 1969 Dealer SPECS guide that may be helpful.