This is an ignorant question, but in what year did Alembic start using the dual truss rods?
Mike

Mike,
My '77 has the dual truss rod system. I owned a '75 that had a single, not sure about '76.  
Best Wishes,
-Ed

My first Alembic, which I'd received in June 1976 directly from Alembic (#AC 76 405, a very customized short-scale w/Series II Electronics) had a single truss rod. I think it's safe to say that the change from single to double occurred sometime in the area between late '76 and early '77.
-Will Gunn

My '75 doubleneck has a single truss rod for the fretless and dual truss rods for the 30 scale baritone neck, so put that date back to at least '75.

birthdate: 8/19/76
 

 
Bill, tgo

There is a post partway down the page here by dela217 that states that dual trussrods didn't become standard until late 1977, although they showed up here and there before then.

I think it's safe to say that they changed somewhere between '75 and '77.
 
My '75 SI has a single rod, and seems no less stable for it.

The necks seem to have also gotten appreciably bigger in cross-section when the dual trussrods came onto the scene.  Some of the earlier single-truss basses I've had the pleasure of fondling sported very thin necks..  
 
John