There was really not a lot to this piece.  I found an old coin door on eBay for about $15. It was a bit rusty, but had the same look and feel as the Happs Controls Over/Under and a heck of a lot cheaper than the $85 price tag.

I ended up sanding down the rust quite a bit and painting the surface black. To get the mechanisms to work, I had to make some modifications to the coin slots (took about an hour to figure out how the coin triggered the switch). Once complete, the quarters were triggering the credits in MAME and all was well.

Here are some images from the coin door close up. Click the image for a larger view.