Yep, most of those were prints, via internegs, from Kodachrome 25. The 64 ASA Kodachrome wasn't around then. Being a 'slow' film speed, and with mutliple layers of colour dyes, colour couplers and so on, the resolution was superb, and colour quality excellent. Outside of the USA, only Kodak plants were allowed to process the film, as the processing was very critical, and needed to be the same quality everywhere in the World, mainly for professional / commercial users.
If I had a £ for every roll I handled during my time with the 'Big Yellow Box', I'd be a very rich man!
So, I wonder what's happening at the Rochester, NY, plant now?