Does anyone know this guitar? I can't seem to find an image of the front - is it possibly an early Alembic rebranded by Irwin (the brass plate on the back seems like a clue to that effect).

Not the same guitar, but possibly related- 

https://club.alembicguitars.com/instruments-customized-by-alembic/missing-link!/

Cute Bluesbird!

Looking at the body on the LP-style thing, I'm wondering if it could be entirely Alembic/employee built - the back looks bound, and it appears to be made of nice-quality walnut, and the cutaway is too narrow to be a Les Paul Professional.

Just an observation... the hammered brass backplate and headstock pattern suggests older/earlier, if employee-made. Maybe someone got ahold of a walnut LP Custom that was decapitated beyond fixin' and had a new neck made? It's a mystery. 

Of the walnut body Les Paul guitars I'm familiar with, this one doesn't fit. Could be a combination of a rebuild and customization. Gibson made a couple different runs of walnut Les Paul, and SG guitars in the later 70's. I just... my spidey sense says this isn't/wasn't one of those. 

The size of the cavity plate in the upper bout suggests some interesting electronics.

I did "sound consulting" for a fool trying to be an impresario & put together an all-girl rock band (hey, free weed is free weed.....); didn't take off, as his real dream was fame, fortune, and unlimited sex - and none of the girls were that desperate. (This was the heyday of the Runaways, Bangles, Go-Gos, Vixons, Slits, etc.)

But he did buy the guitar players a The SG Firebrand & a The Paul Firebrand* (and repeatedly and proudly made it know that he'd paid list for them.....); guitarist for Vanessa Davis Band spent a lot of his time on a non-Firebrand The SG.

This reminds me of absolutely none of them; Gibson didn't put wood that pretty on budget models.

*The bassist - who was actually pretty good - and pretty pretty - declined his largess to play her own Ric 3001; nice bass you never hear of.
In short - I don't think this is a Gibson (closer to a Professional, Personal, or Recording than one of the "The"s, but not quite one of those, either.
I wanna see the front!

Peter