I would venture that it's extremely unlikely you'll ever get a definitive answer to that question. We know he died in 2007, and had continued working until Parkinson's Disease prevented him from doing so. Given that Parkinson's can follow a long drawn out course, it's probable that he didn't just suddenly stop, but gradually wound down.
The above is an extract from a tribute article about Swann in The Times, 21.7.07.
Incidentally, you've probably cottoned on anyway by now, in view of subsequent posts, but in answer to your question of 3.8.18, I'd say the cabinet you posted was made by Rob Davis who does now make cabinets by appointment to the Royal Mint. I've got one myself, and given the superb quality of his work, it's absolutely no surprise to me that he's landed such a plum contract.