I had a round up of all my stray "Bellota" 8007 Spanish made slip fit claw hammer heads that I've picked up over the years, I'd noticed that there were more sizes than I initially thought, when I got them all together (pictured) there were only two pairs the same, the two largest with handles & the heads to their right.
So out of these 12 heads 10 are different shapes or weighs.....a bit surprising.....
They have been produced for many years & six different weights are still available, so some of these are different models/weights, some will be the same model but different year castings. Handles are round or oval cross section, I believe the oval cross section is the most recent.