Brazil • 10 Cruzeiros KM# 619

Hi

Many catalogs, including Numista, report these data:
KM#619.1 1990, 1991 22.5mm, 4.36g, 1.4mm
KM#619.2 1991, 1992 22.5mm, 3.74g, 1.2mm

But mine have different data:

 

The weight can fluctuate by a few tenths of a gram due to the precision of the scale; but the thickness doesn't. The caliber can't be wrong.
 

Can anyone confirm the correct thickness?

Thank you

Thicknesses reported in Numista are primarily user measured and are subject to large variations depending on who, how and where they are measured, on the condition of the coin and on the ability of the person measuring.  If measured on the very thin rim which wears away first before the field wears they there will be a large variation depending on the condition of the coin measured. Measurement on my coin 1990 (AU condition) gave a thickness of 1.75 mm at the rim and 1.48 mm at the center.  Thicknesses in Numista for modern coins should basically be ignored as they are in general unreliable.  There's a reason you can't use thickness to search for in Numista.

So…there is no “correct” thickness.

My 3 coins

Sjoelund

My 3 coins

So whoever measured 1.40 mm for this coin either measured a thin planchet coin or a worn thick planchet coin or measured a thick planchet coin in the middle, hence my comment, “there is no ”correct" thickness."  Numista gives zero guidance on how or where to measure thicknesses. 

Screenshot from 2017:

and from 2020:

Somebody submitted a CR to change from 1.78 to 1.40 which was approved.

I've always thought that thickness was measured by the edge and with UNC coins.
If I have a worn coin, I don't impose my thickness on Numista.
Anyway, I accept this statement:
"So…there is no “correct” thickness."
But I'm baffled.

Thank you

Heligal

I've always thought that thickness was measured by the edge and with UNC coins.
If I have a worn coin, I don't impose my thickness on Numista.
Anyway, I accept this statement:
"So…there is no “correct” thickness."
But I'm baffled.

Thank you

Yes you're right. Thickness should be measured that way. But with anyone able to submit a change request where is the assurance it is always done that way?  Maybe the person who submitted the request to change from 1.78 mm to 1.40 mm was measuring a thin planchet variety and didn't realize it so didn't change the weight also or was measuring a worn thick planchet or who knows what?

I would suggest either you or @Sjoelund submit a CR to change back to 1.7 mm and add into the Comments section the weight/thickness for KM# 619.2 is …  so it doesn't get screwed up again by somebody else. Also, check this statement already there. “In 1991, it has two variations, one with a thick planchet (1.40 mm, 4.36 g) and one with a thin planchet (1.20 mm, 3.74 g).” In this sentence the thickness of the planchet may actually be the thickness of the starting blank before the edge is formed.

@adanieluy  agree?

I have made the CR, with this thread as source!

A friend of mine uses to say “All religions are true”. This is a sarcastic joke, meaning if all are true, but they are different, then most or none ca be true. Beware this is not a discussion about religions, just the implied meaning of a phrase.

Well about the subject of this thread, yes Numista does not instruct how to measure the thickness of a coin, and depending on how you do it and the worn degree, there will be variations.

I think most of catalogs don't give thickness, but of course is a valuable data, since it would be useful to calculate volume when you want to find the density of a coin; that may suggest the metal or alloy used in it. But, the “in water” measurement (don't know if it has a name) is more accurate, cause of coins (medals, tokens, etc.) surface is not flat. Using thickness for this calculation should be calculating an average on different parts of the coin.

As I heard, the raised edge of a coin was create with the main purpose of allow to pile the coins making a “stable tower”, and secondarily to avoid details of the coins touch flat surfaces so the wear of them is minimal. That said, we should assume the thickness of edge is the maximum.

Other important point is the instrument used for measure, calliper or “micrómetro” (in spanish, not of sure the English name for it.

Calliper would give the maximal thickness between the jaws of the instrument, while the micrómetro will give the thickness of the point where you try it.

I have al old steel calliper heritaged from my old job, that I think is very accurate, and more than fit for this use, a digital one, but jaws are made of plastic, so not sure of accuracy, and two or three plastic cheap callipers that will give very vague  reading. And I have two micrómetros; one old full metal, with cricket to avoid measure difference by pressure, but gives reading in 1000ths of inch (in our country we used metrical system, so I need to convert reading), that I feel is very accurate, and a digital one, that generally gives same reading as the other.

Now, back to the subject of this thread, page was created on 2008, on 2011 was added the thickness (1.78mm) and on 2020 was changed to current data (1.4mm), and also included the image of Bentes catalog that stats the variations are 1.4mm on 1990 and 1991 issues, and 1.2mm on 1991 and 1992.

Obviously, sometimes we find some differences on catalogs, and this seems to be one of them, Heligal coins give 1.76 to 1.84mm for thick planchet, and 1.62 for thin; Sjoelund 1.70 to 1.74 for thick and 1.49 for thin, and mine are 1.71 to 1.74 (not sure where I have my thin coins).

About the technical data of Numista, is stated we should put description, lettering, etc. from the coin shown on the main image (top), so I guess also technical data should also describe the shown coin. We have where, in case of variations to describe them; comments section, variety lines and now examples.

Therefore, in a few time I will add some explanation on the discrepancies detected to comments section. In the meanwhile, please let me know if there are some other opinions about this issue.

Thank you. Very detailed discussion. Just as a point of reference if you calculate the thickness given the weight (4.36 g or 3.74 g), diameter (2.25 cm) and density of stainless steel (7.85 g/cc) assuming a cylinder you get the following:

Weight 4.36 g → 0.140 cm = 1.40 mm (what is currently on the page and very close to what I measured at the center of my coin)

Weight 3.74 g → 0.120 cm = 1.20 mm

This tell me that my comment about blank (no rim) and planchet (blank plus rim) is correct and explains why the Bentes catalog (blank thickness) does not match thicknesses of the coins (rim).