In 1926 Rudolph C G Staats-Oels filed a patent for an improvement in safety razors. I’m not sure how much of an improvement it was. It was certainly novel, by the standards of the day. For starters, it was a slant. Or as the patent put it, it had a head:
Continue reading…wherein the transverse curvature of the blade will be gradually increased from one end toward the other thereof.
From US patent 1,633,139