I would love to know more about this. The South African Police requirement for something like this would have been bizarre as it was very much still a 'paramilitary' police service at that time, with its own artillery still.
In South Africa we still don't have a restriction on barrel length for rifles, so the to doesn't fit in. IIRC there wasn't even a requirement for licensing firearms at that time.
In my opinion this wasn't official South African Police, but something else.