Apologies for the very late reply, but thank you paddywhack for doing all that research, very interesting!
Leigh Kitchen, here's a better picture of the clasp, still works fine. Is that what you mean?
Also I've decided to sell this set, what would be the best way to do that, ebay I guess? From what I've read here and elsewhere I gathered 350£ would be a decent (starting) price, does that seem right?