While scales can be replaced, original ones in good condition add value.

Avoid blades with rust or deep "pitting" (small holes eaten into the steel) on or near the cutting edge. As a rule of thumb, the blade should be clear of rust at least 3mm above the edge to allow for future sharpenings.

Tips for Buying a Vintage Straight Razor - Kent of Inglewood

It must be free of major chips, cracks, or bends. While tiny nicks (under 1mm) can be honed out, doing so reduces the blade's width and lifespan.