DIfferent Pinion Nut on 12 bolt

[blackss69]

I have a 69 Camaro SS 350 with original 12 bolt rear end.  I recently replaced the pinion seal.  I noticed the pinion nut (right side) is different than the normal pinion nut (left side).  The nut is zinc plated flange nut with serrations on the bottom.  There was no washer under the nut.  It i[is 3/4 inch tall and 1 7/16 inch diameter (same diameter as thick nut normally used).   I reused the nut that I had marked.   I don't think any rear end work was done on the car as it has been in the family since new.  Does anyone have a part number on this different style pinion nut?

I've used the Attach: function to try to get the picture online.  If this doesn't work will someone tell me how to include pictures. 


Thanks   

[zman1969]

I'd say the left was original GM and the right is aftermarket not original to the car