Thank you so much for posting these. I have looked at them all (these and of Orizaba - and voted four stars for each). The mountains are still beautiful, but man! compared to then, enhanced by the old culture of Mexico...looks wonderful.
Popo will still get snow like that, though not so often so low (though during the winter, it will still snow heavily in the pass, once in a while). But yes, it generally melts pretty quickly with its current activity.
It appears that you climbed Orizaba from the south? Whereas i'm accustomed to it from the north, but even then, it appears there were good snow fields or even glaciers on the south side, in the 50's?
Just below the crater Popo then had a small glacier with crevasses visible from Tlamacas. This photo was taken at the end of the rainy season in October. When it rains below twelve thousand feet, it snows above that altitude.
You're right, I did climb Orizaba from the south twice. The southern side offers a more direct route to the highest point on Orizaba's crater(see previous photo).