How much did you pay for it? I've never seen this style machine ever, but apparently there's a series of them including "Film Stars, Bomber Command," and more.
I found a large collection here and extracted two photos of what your machine looked like before it got modified, or "modified back." I'm reading more on Tom Bolland revamps...
https://penny-arcade.info/the-tom-boland-collectionPlease pull out the mechanism and post a few photos, front and back.
I'm wondering if the entire mechanism was replaced with a "standard" three reel mech. I'm not exactly sure how the original one worked. I'll send out a message to Monti at "Coinopcollectorforum.com" and get him to respond here. If you do a search there, you'll get some more information as well. And, I'd recommend to join that forum since it's much more oriented toward mechanical machines.