Look at the "spine" (the thick top part of the blade). If it has a large, flat, uneven area, it indicates the razor has been excessively or poorly sharpened and may be near the end of its life.
Tips for Buying a Vintage Straight Razor - Kent of Inglewood how to buy a vintage straight razor
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. Look at the "spine" (the thick top part of the blade)
The blade's condition is the most critical factor. Many aesthetic flaws can be polished out, but structural damage often makes a razor a "lost cause". While tiny nicks (under 1mm) can be honed
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.
Buying a vintage straight razor is a high-reward way to get a premium shaving experience at a fraction of the cost of modern custom blades. However, because you are dealing with decades-old steel, you must prioritize structural integrity over aesthetics. 1. What to Look for in the Blade