I am about to start a restoration of a basket-case Norton Atlas. The slimline featherbed frame has a frame number 20/105*** and this has me a bit concerned. Information I have seen elsewhere suggests that Atlas frames started at 20/108000. Could this refer to only UK Atlases? I have seen Atlas crankcases for sale on the US Ebay with numbers starting 20/105*** so might my bike have been a US import? I have no documentation with the bike. Can anyone clarify this?