Can someone tell me if this is a GX head?

Looking at the combustion chamber I say no. Looks like a standard A14/A15 head with low comp combustion chamber.

its hard to tell but i think it actually looks like a high comp head. not sure on the gx or not tho...

This is a pic of a GX head if it helps.



And Lag could be right....it's a little tricky to tell the volume of the combustion chamber.

Does it have an "H" number? Is the eveidence of 4 H20 galleries under the intake ports or 3?

Have a look under the inlet ports. The 1200 & A12 GX heads had four large holes under the ports as per the photo.
They also came with 29 & 35mm valves.

The later, regular A14/15 heads had three small holes under the four ports. They also had 30 & 37mm valves. I can see that the coolant holes under the ports have been blocked off, but you should be able to see what had been there originally.

Did the A14 GX head have four coolant holes under the ports? I do not know, but I suspect that the A14 GX head was a regular A14 head with dual valve springs.

This mythical A14GX, which cars were these fitted to? Were they equiped with the twin Hitachi variable main jet carbs? (SU Style)

Here is some more pics