Could have the Mk IIs armed with the 25pdr HESH, and the Mk I without? Just as an added point of differentiation
Not sure if I’ve ever seen HESH be mentioned but it’s possible that it was done but I’d want to find proof of that just to verify the information
Per below links, a squash head shell was used by 25 pdr guns. These were issued to replace AP after the war, and the Sexton was in service throughout the 50s.
One of the French coastal vessels just got what I think is the first 25pdr in the game, and it does have AP. But being a quick firing naval gun version I’m not sure its AP has as much pen as something like the Sexton would have.