Too bad Michael Petrov is no longer with us, I saw your photos and reflexively looked down to see if he'd posted yet (
http://finegunmaking.com/page33/page25/page25.html).
For what it's worth, I have a Sedgely 'style' Springfield that looks similar. The barrel has an "IJ", WWII 03 replacement barrel.
Edit - dug this out of an old thread from a few years back.
Does yours have anything stamped in the bolt track on the receiver tang (Sedgely serial numbered their's there, IIRC).
A few years ago had a conversation Melvin Johnson's son. He claimed that his pop had a shop in western CT after the war, where they made 'some' (number unknown) Sedgely style rifles.
