This is a very niche question and I知 sure it will take someone very knowledgeable to answer it, but I知 looking to acquire a mk1 airsporter in .177, but am aware there are variations even within the mk1, which seem to correspond to serial numbers.

Differences seem to include the shape and quality of the cocking lever handgrip and cocking latch, and the power/cylinder volume. I believe, and correct me if I知 wrong, that they started off with the serial number E, and then EA, then EB and finally EC.

The earliest version E had less power, a rounded latch and solid cocking grip and was called the Club.
The latest version EC had more power from a bigger cylinder, and presumably cheaper parts for the latch and the lever grip, with the grip having a groove in the middle and the latch being edgier and less rounded.

My question is when did the changes take place? I suppose I am especially interested in the EA and EB. And which is the best?