Cylinder heads - how can I tell if they are Mk1 or Mk2

[sujitroy]

A pair of heads I bought off ebay have all markings including part no. polished / buffed out. Without parts numbers. what other ways can I tell if they are a Mk1 or Mk2?

I seem to recall some thread that the volume of fuel it holds in the valve area is one way to tell. but cant find the thread.

Any other simpler way?
Sujit

[new to this]

Look on the side of the head, theres stamping in the metal V31++ is Mk1 and V32++ is Mk2

Dave