Google Remington scoremaster model 511. Several websites have information on this .22 firearm.
Try e-gunparts.com
Means it was made in February 1942. See related links.
Brownells Montezuma, Iowa
50-250 USD
The manufacture date on the gun itself is WTT. The W indicates the month of August and the TT indicates the year of 1948. Hence August 1948 is the date your model 511 was born.
I bought mine on August 15, 1992 and at that time it was a state of the art unit and is still operating well.
xx is 1951 but there is no month code y (blackpowderx) are the valid letters for month.
Remington Arms introduced this model in 1939 and discontinued production in 1963 with an approximate number of 381,267, units built. The codes AG would place the manufactured date to March of 1960.
I bought a Remington 511-X (1964) this week at a pawn shop. I paid $175. There was a copy of a gun Blue Book on the counter, maybe not the latest edition, but it listed the 5411-X at about $175 for 80% finish, IIRC.
midwayusa.com product #698420 $20 + shipping phone # 1-800-243-3220
It's November 1941 or 1963 depending on if it's fairly low serial or a very high one, that date is either third year or last year production.