Found it, In the Bailey's Northern directory 1781 is George Smith as a razor and penknife cutler, Smithfield, Sheffield

And in the article of Lummus there is a razor (that looks a bit younger, not sure...) of around 1775, George Smith & sons, Sheffield,
1770 - 1785, Trademark, cross and "Smith"
I can only presume that Lummus means that George Smith & sons was in business 1770 - 1785 (and that George died in 1785, which
is maybe confirmed by George being in the directory 1781, and Thomas in the directory 1787 with the mark cross and "Smith")

So George Smith alone could mark its products with cross + smith, earlier than 1770

Having said this, Lummus also talks about razors in the Revolutionary time, having a slight hollow in the back of the back of the blade, near the toe. Revolutionary time is 1763 - 1787 if I'm right...

Making this razor dated between 1760 - 1780 ???