Yep totally fine and too be expected
The hero helmets were made from ABS but the stunts from HDPE
This behaves differently to ABS and is more elastic, so you see more of the little bumps etc.
HIPS is much the same, it will seek out all the detail.
The thinner the plastic, the more detailed the end result will be.
We're not sure if a new mould was used in 76 for the later ABS heroes or not, (ears yes) but the different plastic explains why they don't look identical, regardless.
But as Dash said, it's fine just thought you'd like a quick lesson in plastics
Edit: ah sorry. I couldnt see the pic cos of my iPhone.
That's a bad mould an the owner should brush that up I feel. 5 minutes work