It's an exported machine made by Mills, I'd guess in the 70's. Many of these came back to the USA and were converted to US coinage.
It appears to have an electric solenoid that releases the handle once the coin is inserted. I need a better photo.
If the reels strips were changed, for whatever reason, that could explain the seemingly random payouts.
The handle release may have just been jimmied to work without coins.
When you get it, post a large photo of the inside.
It's also likely this thing was 220VAC so there may be a large step-down transformer inside so that it can run off 110VAC. Be careful in that area, when plugged in.
How much did you pay for it?