Has anyone ever seen blue lines or highlights on some of your coins? I use a digital microscope, but the blue highlights are not on all the coins. Just on some. It looks like this…
It's probably a toning reflection. By that I mean that the light is reflecting from those areas with a blue tint due to the spectrum of the lights, the angle and the unique toning of the individual coin. Try moving the light and/or different lights and see if the blue lines go away. I doubt it's anything to do with the minting of the coin.
This penny I measured to be 18.98 mm. Is this the exact diameter? Or am I reading this scale wrong? And is a Penny supposed to be 19mm?
Your talking about 00.02 ya think that's close enough? It's close enough for me and I don't even know when you last calibrated your micrometer Just a thought, did you check more than one spot and average the readings?
Lighting does weird things, especially when taking photos. Is the blue line there if you look at the dime under a loupe……probably not. Like @Publius2 said it’s probably a reflection from toning or an artifact of lighting.
The funny thing is, some coins have the blue lines, some do not. And it is all look at under my digital microscope next to my computer. If I put my hand over the right of my coin, it DOES disappear.