Thanks Esveka, that's interesting. I based my research on analysis of British newspaper advertising and it seems that the term "Mappin's shilling razor" is found first in 1855 and its frequency rises to a peak in 1857-58. Admittedly, advertising is only a proxy for the actual history. To be more accurate we would have to have access to company records and I don't know whether these have survived. Does anyone in the UK know?