Electronic stylus force gauge question

I prefer the good old analog VTF gauge. I can see the counterweight and I know it works, but the scale shown on eBay intrigues me. I suggest for calibration purposes using a brand new shiny penny. The new pennies weigh 2.500 grams. That is close to the VTF values we all seek. Just get a new, untouched penny from the bank, don't touch it with fingers and get oils on it, or clean with alcohol first and see how accurate your gauge is with that.

Here is another thought as a way to check the condition of your tonearm bearings in the vertical direction. After placing the stylus on your VTF gage and getting a reading, apply a light pressure downward on your counterweight to bring the VTF to near zero and then let go. If the scale has a new reading, that difference is called hysteresis. e.g. let's say your scale reads 1.5g and then you apply a pressure to your counterweight until the scale reads near zero, let go and now the scale reads 1.49g. The hysteresis is the percent difference or in this case 0.67%. For mechanical systems, up to 1% hysteresis is very good. Up to 2% is ok, but considering the quality of our tonearms and bearings used, I would expect it to be less than 1%. Try it in the other direction too. Apply a slight upward pressure on the counterweight to raise VTF by 0.5g or so and then release.
So why is hysteresis a factor? Because as the tonearm/cartridge tracks over a record, any waviness in the record causes the tonearm to move up and down. If the bearings have too much hysteresis then the VTF will be changing slightly- going higher as the tonearm is pushed upward and then being a little lighter as the tonearm comes back down. Aside from inertia, 0% hysteresis means the VTF would stay constant as the stylus tracks over a wavy record.
The scale itself should have extremely low hysteresis since it is a strain gage. Good quality scales that I have used change maybe one digit out to the third decimal place when I have added/subtracted the load slightly.