Thanks to Kuduae's excellent help, I think we might have the makers name; Helmut Strugger. He was based in Bad Goisern, Austria, which seems to be where the rifle was both made and purchased by a friend of the gunsmith's family, then given to a son as a going away present when he moved to New Zealand, (to work as a chef in Franz Josef township in Westland).

I'm following up a lead that could help finally settle this in a few days time. But for the moment, this is the only gunsmith with "HS" initials in this area. Photo follows.