Odd Rem 513T puzzle?

TRAP55

I have a Remington Model 513T, with a receiver marked U.S. 202055, and a barrel date code I can't ID.
Left side:
All in the same font is "U UN 31".
Three letter codes are first letter = Month.
Following two letters = Year.
Number suffix is an assembly number, but the letters don't make sense.
Right side:
R.E.P. in an oval (Remington Proof)
3 leaf clover
Something that looks like an "X". The top left, and bottom right of the X have the ends curved, like a long skinny "S"
Some other odd things on this rifle,
The receiver is grooved for scope rings, I've never seen one with scope ring grooves. This barrel and all the other ones I've seen are tapped for scope mounts.
The receiver looks like it was made for a tube feed, identical to a Model 512 receiver. A 512 receiver used to fill a government 513T contract?
The bolt is electro penciled with (I guess) another serial number, and the bolt handle has a copper band with the same number stamped on it.
Any ideas?

rufe-snow

Kind of confusing? It sounds from your description, like a military trainer, made during the war. But I believe they were marked, "U.S. Property?

There are at least two forums I am aware of, that have boards specializing in .22 trainers. If all else fails try them.

One is on Gunboards, the other Rimfire Central.

TRAP55

Rufe, that's another oddity, just the US stamp. But...if they weren't an Army Trainer, they wouldn't have a serial number.
Thanks, Rimfire Central was going to be my next stop is I couldn't get any info here.

TriumphGuy

R.E.P. is an acronym for Remington English Proof. I don't know how Remington got started using "English" in their proof markings. I have seen it on many, many Remington firearms. I wrote a letter to Remington 50 years ago asking them for the provenance of an inherited Model 14 pump that had the R.E.P. barrel marking. I got a nice letter of explanation back from Remington with year of manufacture (1914), etc.