Edge tools are comparatively simple to grade for condition as they have substantially only two parts, the blade and the handle.
Handles are often replaced over the life of the tool. Whether they are early proper replacements or originals is difficult to establish and makes little difference in price. Any proper replacement handle is acceptable for the grade of GOOD. However, heavy pitting, significant metal cracks, or excessive wear of the blade will downgrade the tool to GOOD MINUS or below.
A "laid-on" steel edge has more value than the later all-cast or all-forged steel baldes. The laid-on demarcation line is almost always visible on one side at least. For tools without handles, or handles nearly worthless, the pricing should be reduced by 1/3 to 1/2.
Those edge tools that are signed will generally be at the uper end of the grade price range. In the case of desireable makers, the price could go above the top of the range.