MGB head identification

["Charley Robinson" <charleyrob@charter.net>]

I recently acquired an 18V MGB engine with a head that has the number on it
of "12H2923" on the top line and right under that is "AFIH". The MGB
Cylinder Head Cross Reference chart I have doesn't show this number. Does
anyone have any info on whether this is an original B head or what it might
have come off of? 

I've been told the engine is a gold seal factory rebuild. Does anyone know
where I can find out more information on this?

TIA,

Charley Robinson
1954 MGTF
1957 MGA