There were no real differences in steel and quality.
But in finish there were two types . One ,the more common smoothly polished receiver and some less desirable with a rougher (looks like sandblasted)receiver.The added pictures will show the difference.
Following the Czech proof date the rough finish were earlier productions.
But is difficult to pin down "best production years".
Two types in triggers: Double stage and single stage.The single stage more desirable in my eyes.
All the rest depends on what you prefer and the individual state of the rifle.
There were different style of stocks and 55 and 60 cm barrel length and shape.
Luckily You live in a country where it is relative easy to find the desired specimen.