Yes the neck stamp looks authentic. However, the routes in the lower part of the body are not consistent with mustang bodies .. nor the routes around the bridge area. Also you can see it originally had 2 single coils.
Most bronco and musicmaster bodies I've seen also don't have that lower route. And the duosonic has a small route down from the neck pickup cavity for the switch in that area. So can't even guess that it would be one of those.
I'll put your image up on our facebook page and see if anyone can help ID the body.
Here's what mustang body routes generally look like. There are always exceptions and this one has the area enlarged for a humbucker in the bridge.
