Officially, Leica only made 5 MD 22 cameras (1/2 frame MD-2) - 2 were dissassembled and "lost. However, they made a lot of the body castings and those were later disposed of. The M4P 18x24 was never an official camera and most, if not all of them were assembled in Japan and in the UK. I have even seen a olive green M4 P 1/2 frame in Hong Kong and also a black paint one.
Some of these had masked filmgates that only exposed 1/2 frame, with the 2nd 1/2 blank. The gate on the one for sale looks like a standard, centered one. The wide spacing was done on purpose. With some of the Md-2 cameras you could use small, plastic bars that could be inserted through a slot in the baseplate. You could do notes on these and when printed, they would show up. Most of the 1/2 frames were designated for use on microscopes, CRT recording devices etc. On the camera for sale, there seems to be no indication wether it has the correct bright lines for the 18x24 format.
Leica Midland would do "custom" cameras if you wanted it and could handle the cost and as they were rather sloppy with record keeping - some of these "specials" are proper factory output - but most of them were assembled by technicians outside of the 'proper" Leica channels.