I can offer some support for the conclusion that the buckle is ERII and post-1953. I have three assegais that were made in the mid-1950's by the last traditional Zulu blacksmith in the Bushman's River valley of Natal. His forge must have been in the same general area as the one reported by Ken Gillings and they could in fact be one and the same.
Also, Ken's forge is in remarkably good condition and this may be a reflection of its relatively young age. On most Zulu Iron Age sites it is only iron slag and fragments of flues that reveal the former presence of forges.
I know that some (?many, ?most) members of the new Zulu elite are not keen to be reminded of their Iron Age ancestors, but I wonder if one of them might not be interested in giving the blacksmith site some kind of acknowledgement and protection. Also, the Natal Museum in Pietermaritzburg is (or was) a centre for Iron Age studies, so reporting the find of the forge to this institution might help in its future protection.