I'm not sure of the chronology of the suffixes, believe the "60" series date from that era from when they were introduced.
I've owned a LOT of Weaver scopes and I've had mixed results. I've had 3 of them shoot the lenses in the ocular loose. One was a V4.5 that gave up the ghost after a year on my 375 H&H, still functioned, just the rear lenses would rattle back and forth about an inch. Obviously it wasn't water tight either.
Had the same thing happen to a K2.5X on the same rifle. The V4.5 had less than 2000 rounds under it when it let go, and I'd bought it new (about 3 years before Weaver closed their doors). The K2.5 went with less than 1000 rounds under it. Last was a K3 on my beloved old .444, took a while, but it shot loose too.
The K and V series weren't noted for being fog/water proof, in fact I don't think they were sealed and purged. They were also only magnesium flouride coated, not multi-coated so light transmission isn't the greatest when new, and as he scope ages and the coatings begin to flake it goes down hill too. Still for all their faults, they were an OK scope in their day. With the 3 bad ones in the mix, I still had/have probably 25 decent ones.