It's older'n you an' me
both. Rough guess of late 1800s, back when most of the horizontal mills were made from lathe headstocks.
The motor and whatnot are almost certainly later add-ons, to be able to use it by itself, rather than attached to an overhead line-shaft system. (Note the jackshaft uses vee belts.)
Couldn't say on the make and model, but one identifier might be that collet. It's hard to tell the scale, but if that's a 5C collet, that'd narrow it down quite a bit. I think the 5C came out in around 1890-ish, and for the longest while, was pretty much limited to pre-Hardinge Cataract lathes. (That's where the "C" comes from, by the way.)
Of course, the spindle could have been re-fitted years later, so even that's no proof...
I'm not helping much, am I?
Doc.