I was looking for the thread that had the GT with the non stamped rear bologna cut and could not find it to add this..
Peugeot Auction
Here's a Peugeot bmx frame that looks damn close to the mach one frames from the same time.

It has the right geometry and the freestyle dropouts on the rear triangle.

The bologna cut top tube terminator is suspiciously close too.. Was this made in the same factory?

As even says "Sae 4130 Ishiwata CrMo"
Anyone know what the name of any of the GT factories were?

I would think that this came right down the same line looking at it.
Never seen one before, but it's so similar, it would have to be from the same materials no?

Other than the front edge of the drop outs being angled inward and the brake cable clips, it does look identical. Good eye.

Well the dropouts are identical to the 85/86 overseas performers and Pro Perfs, but not drilled, and there's the addition of the chain guard tab too.

It's interesting though none the less.