Odd cylinder head

[Gt6steve@aol.com]

Amici,
I brought home a six cylinder head last night.  Looks like the ordinary TR6 
head except it has an extra cooling water tap directly above the #5 exhaust 
port.  It's marked with number 219019.  Can anyone identify this?
The reason I ask is that it came from a basket case TVR 2500M.  I'm wondering 
if they did a special head just for TVR.
Thanx, Steve Smith