I'm planning on buying the NPM in these pics but I have never seen a light gray finish like this before. Is there any thing anyone can tell me about it? Thanks for your help and expertise.

Probably a post war arsenal refinish. The various arsenals that refurbed carbines used various park colors. From the pics I'd say RIA ( Rock Island Arsenal). Any arsenal refurb marks on stock...if its the orig stock that is ..... ?

Anniston used a light grey parkerizing, RIA also used light grey than later on used a clear park solution without dye so thiers looks silvery light grey to a almost galvinized look. Most of the others offhand that I can recall  used shades of green park.

Stock has no marks on it other than the IO in the sling well.

I have an inland receiver that looks exactly the same color.

I'm going to go ahead with the transaction.  Its one of the best condition carbines I have ever seen and it comes with the bayonet pictured below. The NPM carbine and included bayonet look at least twice as nice as my Quality Hardware carbine and current bayonet.