I picked up another Simplex the other day. I'll try and post a picture of the frame number. It took me a while to figure out what happened when they stamped it but I think I did.
Frame number is 07751, the 5 looks like a backwards "C" and only half the size of the other numbers. I believe the stamp drifted up on the person stamping it and when he hit it with his hammer it only stamped the bottom of a 5.
I'm taking the motor to Wayne tomorrow and have him go through it.

It's an automatic.
I think it's been pieced together and I've already got the motor and tranny pulled off the bike.
I'll try and post some pics tomorrow.