Pulling a dragnet across the web brings up some interesting titbits now and then, and the 1762 Perrett’s safety razor is one of them.

By placing a wooden guard around an ordinary straight razor, in such a manner that only a sliver of the edge protruded, you were at least sure not to slice your ear or nose off while shaving. Still a far cry from the more modern DE and SE razors, but from what I can tell it was the very first baby step towards the razors we know and love. The basic idea was copied and expanded upon for the next hundred or so years.