In regard to the month/year stamp I shouldn't have said they all have it, what I should have said is all that I've ever looked at have had it, or the remains of it, as the area seems to cop its fair share of hammering over the years. Its small and not easily seen if the area is painted at all. I don't think it was something peculiar to one market and its something I've seen on frames over many years, widelines, slimlines and Manxes. My slimline Mercury has it, so does my 60 Manx, and I checked a 56 Manx this week that had just been imported from the States and it also had a date stamp. I wondered whether it was something put there by the frame makers rather than Norton. No idea really, its just something I've seen over the years.