Turn the motor around 180 deg. in the frame, so that the little "lever" comes out of the "circle" shaped hole on the one side of the frame.
IF after you turn the motor around, the lever does not line up right to come out of the circle hole in the frame, it might be the motor from a different loco put into that frame (You may have to bend it a bit to bring it back true. Should be a straight shot out of the reverse drum then 90 deg-ish bend after clearing the frame). That being said, I have found some that I believe came that way from Ives....where the lever didn't line up to come through the hole, and were bent to make do.... so you never really know.
The reverse lever (and hole in the frame) is usually to the rear of the assembled locomotive and I believe how it came from Ives originally, based on 10 years or so of observations.
It's the frame and motor from an Ives wide gauge 3235 electric type loco (New Haven style box cab).
With the diecast wheels, the shell would most likely be light olive green
OR
Chocolate brown.
both with brass plates.
Circa 1925-1926
PIC of mine, which is an "R" so no reverse lever, but you get the idea.