Suggestion of inprovement, thickness and mass consistency

Hello Numista members.

I was studing some coins and I found this one:

N#330698

This coin has no information of thickness in the catalog. It has 0,4g of mass and 0,9mm of diammeter.

As it is made of silver (about 0.01049g/mm³) and it is a cilinder (near round surface). It means that it has abou 60mm of thickness! 😱. Almost a true “wire” coin 😅

I found this number using the formula = h = 4m/pi * ro * d^2

Where m = 0.4 g pi = 3.1415 ; ro = 0.01049g/mm^3 and d = 0.9 mm for this coin.

This clearly inform a possibly error in the catalog (or the diammeter is wrong, or the wheight is wrong, or the material is wrong). Because the coin clearly has no thickness of 60mm!).

Thinking about it i suggest the following feature to check catalog information: thickness and mass consistation using density:

h = m/(ro*A) where ro is the material density and A is de base area of the coin shape.

Some materials density can easily found on the internet, some exemples here: https://www.engineersedge.com/materials/densities_of_metals_and_elements_table_13976.htm

And the base and volume formulas can be found for exemple here: 
https://en.m.wikipedia.org/wiki/Surface_area

https://www.cuemath.com/volume-formulas/

Best regards 

Turi

My brazilian friend Vladmir gave me another idea. It could be added to the improvents hints feature to the referees indicating possible catalog inconsistents of size, materials and mass.

Putting the decimal in the wrong place for the diameter (i.e. entering it in centimeters rather than millimeters) is fairly common.  That type of error should be caught by the referee prior to validation (and most probably is).   This one slipped through.

rsirian1

Putting the decimal in the wrong place for the diameter (i.e. entering it in centimeters rather than millimeters) is fairly common.  That type of error should be caught by the referee prior to validation (and most probably is).   This one slipped through.

Yes. I agree. Perhaps the user added the thickness in the diammeter field too. It is possible too. The idea is to add another feature to check this mistakes by means of mister Robot and indicate it to the referee in the improvments hints section.

The problem with using the thickness to determine if the diameter/mass/thickness are correct is that the volume calculated is made up of a large portion of air.  

I think the go/no-go limits would have to be broad enough to not flag values that are actually correct.

I assume you're suggesting just a check of the values entered and not artificially calculating a thickness where none has been entered.

rsirian1

The problem with using the thickness to determine if the diameter/mass/thickness are correct is that the volume calculated is made up of a large portion of air.  

 

I think the go/no-go limits would have to be broad enough to not flag values that are actually correct.

 

I assume you're suggesting just a check of the values entered and not artificially calculating a thickness where none has been entered.

Yes. I agree. My suggestion is to use formula calculation to check large deviations, not to calculate the thickness. As in the exemple that I gave above. One coin with 0.9mm of diammeter and 0.4 g whould have 60mm of thickness. A "wire" coin. Stronge suggestion of a wronge data.

Also calculating alloy densities which would be important for auto-flagging is a non trivial thing and real world measurements will always deviate from simplified formulas and theoretical crystal structures (sometimes by quite a lot).

OK. Your suggestion would be good to flag existing coins that should be checked.  My point is that a diameter of 0.9 mm should have been flagged immediately by the referee who accepted it.  I'm not sure getting a ping from Mr. Robot would have done much good.  Out of curiosity I plotted the number of coins in the Numista catalog vs. diameter (≤ x).  Any coin 4.0 mm or less is probably suspect.

So far, hints are checking for:

Banknotes and paper exonumia with lenght smaller than 20mm.

Coins and exonumia with diameter smaller than 5mm.

Coins with diameter smaller than 40mm and weighing more than 250g. (I will set this for exonumia as well soon.)

Do you have any more suggestions?

I gave my friends (engineer and physics teacher) a coin to check diameter/alloy/mass/thickness formula, if it is possible to check and it deviates a lot, simply by a fact that coins are measure at rim, and they are less thick in the centre.