Pellet weight
OK! Clearly looking for the mature shooters here! (or a modern pellet anorak!)
As one of those old enough and who was involved in national and international rifle shooting then, I don't think there was other than 4.5 in those days.
During a clear out a few years back I found an unused tin of 200 Eley match from that period, I think the wife had been given them at the Brits at Cardiff and stuck to her RWS Meisterklugeln. Still have the tin, they are marked No 1 (.177") 4.5 mm. And also have an old pack of 200 Meisterklugeln also marked 4.5mm (not even 4.50). And our earliest test card for a Walther LGV Spezial is just marked 4.5 mm on the calibre and no options on the test group.
I know the wife used RWS Meisterklugeln in her Original 75, and later in her Walther LGR, and the old pack just had 4.5mm, I have no recolection of different sizes, but that could just be the ramblings of an old man, and it could be she just used 4.5?
I think the "selected" 200 packs came first, more concerned about standard and condition than size, that one has now drifted away , with most top level shooters using straight from the tin, or decanting into flat packs.
I think you'll need the pellet anoraks, to answer when the options came in, the best source will be on rifle test cards as they will be defined and dated, I'd guess at late 80's when the rifle techno war really started.
Walther KK500 Alutec expert special - Barnard .223 "wilde" in a Walther KK500 Alutec stock, mmm...tasty!! - Keppeler 6 mmBR with Walther grip and wood! I may be a Walther-phile?