Olympus M-1 with motor drive coupling????

I have several Olympus mechanical bodies, all OMs. I thought I might add an old M-1 for fun. Looking at some that are out there, I see some with the MD cover on the bottom. I did not think M-1s ever had an MD option? Does anyone know?
I think it's possible the M-1 bottom got replaced, or worse, someone put an M-1 top on an OM-1 MD.

What do we know?

I would assume the situation is the same with the replacement for the M-1 - the (non MD) OM-1.
When the OM-1 was originally introduced, there was a factory option available to have the motor drive coupling added. Olympus was surprised at how many customers requested that, so they relatively quickly replaced the OM-1 with the OM-1 MD, which came from the factory with the coupling already installed.
My first OM-1 was purchased new, when the product line change (from OM-1 to OM-1 MD) had not yet made its way to Canadian retailers, but was at least rumoured.

Incredibly, the Olympus M-1 had a very complete line of lenses and accessories listed in the 36 page 'M-1 new name OM-1' brochure, including the Motor Drive Group, offering both a 1-4fps Motor Drive 1, and a 250-exposure capacity motor drive unit. These were all pictured in the brochure, not merely an artist drawing of the accessory lineup. And even the original M-1 brochure shows the 250-exposure magazine and the Motor Drive Group.
It is therefore interesting that two years elapsed between the original OM-1 and the subsequent OM-1MD.