Steamwolf : My Marx reference lists a 494 and a 495 on locomotives that look visually like the one you found. They also offered a similar engine as a 391 Canadian Pacific. The differences are in the stack and domes. Your engine has the single streamline dome and streamlined stack of the 494 and 495 series. The engines were offered as 0-4-0 and 2-4-2's . The last 495 was offered in 1957.
The neatest thing about your loco is the tag. I can see that part of it is imprinted F.O.B. Girard Pa. The Marx factory of course was in Girard and this shows a link to that facility. Maybe you have an engineering sample or prototype of the engine that they derived from the 391 and offered as the 494 and 495. The 496 could just be a working number in engineering.
WHAT A FIND!!
Best Wishes, Don McErlean
