That is a somewhat rare, and today valuable, .22cal Colt Lightning pump/slide action rifle.
Write Colt for a dupe certificate - it'll increase the value a LOT.
Please - DO NOT CLEAN OR otherwise TOUCH that gem with
ANYTHING other than a soft oily cloth, or you could well turn a rifle worth anywhere from $2K-$4K (depending upon the Colt letter) into a $900 shooter.
http://en.wikipedia.org/wiki/Colt_Lightning_Carbine
.