Yes, I think you're right Trev: those dates fit in better with King's pattern as well as the maker.
1836 really is disgracefully behind when you consider that:
Exeter had George IV by at least 1829
Dublin had Geoge IV by at least 1829
Sheffield had William IV by at least 1837
This must be more than a matter of geography. The London assay office didn't get on well with the English provincial offices, but why is Newcastle unique in this respect? I thought it might just be the case with small spoons (which are often left behind in hallmarking developments), but I found George III on an 1827 table fork. Very peculiar.