68' 8 3/4 factory paint marks

[motorhead]

Any of you guys have this "D" on the case of your 8.75 ? My buddy down the road has a 68 GTS and it has the same mark in paint on his (it's one wheel peel) rear. Is this plant specific or something they put on all 68's? This case was preserved under an inch of gear and brake fluid,still has the 3.23 tag and suregrip fill tag ! This is from my 68 Charger R/T if that helps.

[OttawaCharger]

Mine has something like that

[tan top]

my 69 had a yellow B painted on the 8 3/4 housing  i allways thought that the B, was for b body , but it can not be now as you guys have a letter D