Possible USMC match rifle

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Thanks to Mr. Beard and CPLstevenorton, I was given info on how to research this rifle which came home with my granddad after he served in Persia during WWII. The only ting I can attest to is that Gramps had no desire to work on guns, just hunt with the emphasis on after the hunt socializing. The story he told is winning this at a poker game from a marine who claimed it was a USMC match rifle. After doing some research I pulled the stock and was surprised to find all sorts of mods that look like they were done by a professional including turning down and around the rear sight collar. I have more pics if anyone would like to help me piece this piece of histories story.
Came into possession in Persia 1945. No mods made since then.
S/N 236053
S/A star gauge barrel dated 12/27
lyman 17A front sight no manufacturer info on sight
lyman 48C rear sight, again no info other than lyman deer trademark
rock Island r5 bolt, double heat treated in 1918 according to Mr Beards steel chart, in the white.
Straight bolt handle
Serrated trigger
Polished follower
Refinished c Stock
hatcher hole
enlarged hole in bolt
stock has been finely sanded with no cartouche marks other than an S and and a F in the magazine cutoff.
rear of stock shortened by 2 inches.

I know how easy it is to clone a NM and just want to get its history right when I pass it on to my son. Gonna unsporterize it as soon as smith can remove the rear sight collar which was ground down but not off.