I doubt he ceased at all totally. Like many manufacturers, I would not be surprised if he continued to make guns to order for others - after all, business is business.
Robertson would have continued with his manufacturing facility, continued making Boss guns and probably guns for others, in line with his previous practice of making best quality guns for the London Trade. This is only educated speculation, I have no definitive documentation to prove it.
I have come up against a few Robertson guns recently - a 20-bore I just serviced and added a leather pad to for a lady client, a 16 bore which just arrived to be made ready for sale and a .410 in the next Holt's sale.
All boxlock ejectors of good quality. Finding a 12-bore should not be difficult, I see one or two a year; so you could get hold of an interesting Robertson collection if so minded.
Last edited by Small Bore; 07/12/10 07:09 AM.