Strike Depth Measurement?

Just wondering: Is there a strike depth measurement that measures the depth of a strike below the rim, or a relief measurement for the legends and devices of medals and coins?

I only ask since I came upon this text in an historical document:
"...this commemorative medal had a depth of 1000..."
and
"...in 1985, [the mint] produced high-depth, larger medals with a diameter of 65mm and a depth of 5100.

After each number above there is a symbol like a backwards "u". Here are the actual numerals:


Any idea what this measurement is? I think μ is "mu?"

 

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Almost certainly "microns", thousandths of a millimeter -- although 5.1mm seems really deep, even on a large medal?

 

micrometers I'd assume

 

Micro is 1 millionth. https://en.wikipedia.org/wiki/Micro-

 

Yes, microns is the unit of measurement here. And while 5.1 mm may seem really deep... have you ever actually seen some of those high relief medals? The portraits or devices literally *pop* off the surface. The high relief of the best medals is simply stunning.

 

PF, do you know the DEPTH from the rim to the deepest part of the field for the 1907 HR and 1907 UHR ?

And maybe how that compares to more popular/modern coins and/or medals ?

 

I think you got it!

Thank you!

 

Very interesting. And this is/was 35 years ago. Am not familiar with it but it begs the question/consideration for thought: I'm curious what others think of similar, up-to-date computer/digital measurement and assessment...and others of computer analysis...for grading purposes, to eliminate and improve/modernize much of the subjective issues with the process.

 

μ is the standard scientific for millionths (10^-6), as mentioned.
m is already reserved for thousandths, so they had to use Greek letters, I guess.
As a chemist, we would more often use nanometers (10^-9 m) or Angstroms (symbol Å, 10^-10 m). Angstroms happen to be about the scale of atomic bonds.

Anyway, you could use an atomic force microscope to get a very accurate relief profile of a coin without damaging it. I wonder if someone has already done so. Unlike most types of high-resolution microscopy, you don't need a vacuum chamber.

 

That's probably a better question for Roger over on the NGC forum. I have no idea.

 

Couldn't such microscopy also be used in AI grading mentioned by Mac McDonald in #8 above?

 

It's an interesting idea. You could use scans to quantify the amount of wear against a standard. But there are so many other variables about the surface condition which determine value that I don't think the market would accept it. People are very concerned about luster, toning, surface oxidation, etc. And it would probably be too expensive a technique for routine grading.

 

• Last I heard PCGS has the basic patents from 1992. Interesting reads here. lots of info. This one expired. Jim

https://patents.google.com/patent/US5224176A/en

 

You're just reminding me how much I miss @Electron John and his images...

 

Don't worry, when I scrape together an extra $75,000-100,000, one of those puppies is going in my basement. No household should be without an SEM

 

A human hair is 50-90 microns. Wonder if they dropped a decimal point or used the wrong unit letter.

 

I'm further behind. Need to install the basement itself first.

 

Or maybe they had an accurate way to measure?

 

I wouldn't recommend laying a hair on a high relief medal (oils and all), but a truly high relief medal has significantly higher relief than a human hair. Even a typical circulation coin generally has higher relief than a human hair.

 

I think I read that the lettering or devices on the 2009 UHR were 1.4 mm high.