@Buddy
I do not have a clear answer to your question but maybe the following facts will help answering the question.
As from 1965, the 1 Rand was introduced and was all in silver (from 1961 - 1964 no 1 Rand except for the gold 1 Rand)
The last year the Silver rand was minted for circulation was 1976. During 1977 the circulation rand was changed from silver to nickel. All proof sets however, were issued with silver rands and not nickel.
As from 1977 up to 1983 only a few proof nickels were minted ... range between 10 - 15
In my opinion they only minted a few proof nickels as all proof sets contained silver rands.
Hopefully this info is correct and does not sound like a lot of gibberish ....