Unusual Slide Markings

M1 Carbine Slide Saginaw s with Ordinance Mark | eBay

Has anyone seen a Sagunaw (SG) slide marked like this one? It appears to be a (Riesch) Type III slide and the finish looks pretty legit to me but I have never seen an SG (Saginaw plant) slide with an Ordinance acceptance mark or periods in the bottom 'SG' logo stamp. Early production? Transfer from Grand Rapids plant. Any known documentation that I am unaware of? Thoughts or guesses? Chip

My Inland rebuild has a Saginaw slide with the acceptance stamp but I don't remember how the SG is stamped and I'm pretty sure it's not on the outside.