U.S. Army Model 1911 45ACP

I am looking for the value of my model 1911 Army issue 45. It was gifted to me in 1974 by my father in-law who carried it as his MP side-arm during WWII. The serial number 21364 has confirmed the 1913 manufacture date. To my knowledge the only replacement parts are the grips which I replaced myself. My father in-law had clear plastic grips made so he could put family pic's behind them. I still have those also. Also, the serial number is preceded by the alpha letters NU. I have not been able to determine what significance this has. Any help would be greatly appreciated.

hi comanche,
i'm finding nothing on the NU preceding the s/n. i'm still looking but you may have already checked this site out.
http://www.sightm1911.com/1911Production.htm

i'm doing some more research and i'll let you know what i find out.

Kim

the letter may to the inspectors initials proof??a pic might help ..it's a pricey example even in poor condition my books say 1150.00 and can be as high as 4500.00 at auction or for insurance purposes.. so very nice hand me down gift anyway ya look at it!! mabey look at springfield research center online ,,i'll try to get an address...i beleive they still have a inspectors proof marks section,,may tell ya what the NU means,or mabey do a search trying 1911a1 proof markings or serial numbers..
bigcurt

heres a link for springfield reasearch center,,lots of intresting sections and great for gun markings or inspector marks..i did a quic search for your NU but didn't find a inspector proof,,but mabey try the gun markings section http://armscollectors.com/sn/usmilookup.php? file=us_m1911gvt.dat ya may even think about a research letter from them ..
bigcurt