The 60 is a great little gun, quite light, especially if you take off the barrel weight, totally recoilless and perfect for informal short-range shooting. But the breech lockup is a not very robust ball detent so needs to be looked after. The 65 has a breech lock and a much heavier barrel sleeve. It's slightly longer than the 60. Both are capable of 600 fps if in good internal order. The 60 actually outlived the 65 and was still being made alongside the mod. 75.
Prices for each are usually somewhere between about 140 to 250 euros on egun.de, depending on condition.