Well under the rear sight you have Underwood and then the serial number. On the heel of the receiver is a US ordnance bomb. The RIA on the stock means that the stock was on a carbine that went through a rebuild at Rock Island Armory. The stamping on the right side of the stock would be the acceptance stamp and would be for the maker of the carbine. It's very hard to read it in the photo. Look in the sling well for any letters in there. Your carbine was updated and rebuilt during the late 40's and early 50's with the adjustable rear sight and the barrel band with the bayonet lug on it. All parts on a USGI carbine are stamped with letters that indicate who the parts were originally made for. Someone own owned it before had the carbine blued. It would have been parkerized originally. It looks real good and should be a good shooting one.