It seems plausible that both the dt lever bosses and the rear brake cable stop were additions at the time of re-paint.

The headbadge screws don't look original. They could simply be substitutes for original rivets, or I suppose it's possible that someone stuck a MB headbadge on some other frame. I'm not saying that's what I think happened, but in the absence of other Motobecane identifiers, it should at least be considered.

Is there a serial # visible?

It's a cool looking frame in any event.

The rear derailleur angle looks a little funny to me btw. Does it shift OK?