My Singer 15 Gingerbread decaled machine had an electric light in place of the back rear inspection hole. I removed that and replaced it with the proper cover.

But Ron, you're right, there could be a hole under the handwheel. Can't see there in the pics.

deplaylady,
I've seen lights that were installed on that screw but the inspection cover was put back on top of the light bracket. That may have been the "Singer light". Bummer that they just took off your cover. Glad you made it right again!

There is an aftermarket bracket in, black, sheet metal that fastened where your back plate is missing. I have one just like yours. That plate held the light. There was a screw-on motor support (boss) that fastens on the right side. Mine was broken and I was lucky enough to find one at a sewing machine shop. DH is rewiring it for me. They are out there. As many 66s that have been junked, someone will have one. Watch Ebay (sewing machine parts) and junk stores. Good luck

Maybe the motor was one of these:
http://www.quiltingboard.com/vintage...ml#post6370386

You can find the rear covers on Ebay. It keeps lint and dirt our of the mechanism. If you find that too pricey, then use duct tape, cut to size. You don't want stuff getting in there or little fingers.

Is the motor support bracket attached to the inspection hole screw along with the light?