It's on a 1970's Fender P Bass.
 
http://www.ebay.co.uk/itm/Vintage-1975-Fender-P-Bass-Alembic-Bridge-w-TKL-HSC-/310802483567?pt=Guitar&hash=item485d45896f
It looks like a really heavy piece of metal maybe plated brass, Might be a nice mod to your bass Harry.
 
 


 


 
 
Jazzyvee

Possible, but I wonder why they didn't just stick a Bad Ass bridge on it. Very fine routing job, from the look of it. I would be curious to know if the plate was machined out of a solid block of brass, like it looks like. Alembic seems to be set up to work brass more than steel.
 
Takeing a magnet to it would tell.
 
It would add a lot of weight to a bass already known to be heavy.

I have seen a similar version of this type of modification once before in the form of a tail piece and separate bridge.                           The very cool one  that I know of was made by a fellow that once worked at Alembic many years ago ;                                                                    Mr. Frank Fuller.                                                                  
 
(Message edited by sonicus on December 02, 2013)

It does look Alembic, although it doesn't have the alignment pins.
 
Love the amazing levitating bass Wolf!

That looks like a Stars bridge to me.  They sold them chrome plated like that.  If you remove it from the baseplate, the word STARS would be stamped on the underside.

I remember Stars Guitars. I remember Ron Armstrong from Stars Guitars as well as well as others that worked there. I remember when they were at the old Alembic location at 60 Brady St and later moved to 818 Folsom St , both locations  in San Francisco. I went there often back in the day . I remember many of the  various parts that they sold and in fact once owned a Stars Guitars made bass . It was a bolt on neck bass that had a Stars Guitars  bridge on it. The description of the bridge  on my old Stars Guitars bass  would be similar to a Leo Quan  Bad Ass Bridge with their  Stars Guitars Logo on the thick metal mass by the  saddle adjustment screws.   It might be possible that this is a Stars Guitars item as well, ( maybe). They experimented a bit.

Here is a Stars Guitars bridge like on my old Stars Guitars bass ;

Looks like a neat bass! I like the bypass controls & kill switch mods. I'll be passing on it, though must admit I have been tempted to install my Badass II on the AlFemBic. The sad part is, I'd be doing it for looks not sound...