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 Replies: 16 / Views: 1,291 |
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Pillar of the Community
Serbia (Srbija)
576 Posts |
I got an Italian coin of 20 centesimi 1940 magnetic variant with reeded edge (KM#75b) and I noticed that new coin that I got and the one I already had are kinda different.... One is stuck to a magnet like a kid to a Iphone  and the other is sticking so weakly on a magnet that it drops as soon as I lift it from the table... Is this a variation or just .... I dont know why it happens, does it depend on an alloy composition or can a coin lose some of its magnetic property over the years...  |
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Moderator
 United States
188342 Posts |
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Bedrock of the Community
United States
25176 Posts |
Inordinately fascinated by bits of metal with strange markings and figures
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Pillar of the Community
 Serbia (Srbija)
576 Posts |
I know about those variations but both coins are KM#75b
So both magnetic and both with reeded edge its just that one of them is weaker magnetic than the other... so my question is there a variation or something else ?
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Moderator
United States
188342 Posts |
According to the Numista links, the KM# is different for all three. The magnetic status comes from the type of acmonital steel used: ferritic or austenitic (which is paramagnetic). |
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Moderator
Australia
16827 Posts |
Ferromagnetism - the ability of a piece of metal to stick to a magnet - is a property of an alloy; as such, it cannot be "gained" or "lost" without significant chemical alteration eg. if the coin becomes very rusty. Ferromagnetism can weaken under certain conditions eg. if it's heated, but it comes right back again once it cools down.
Don't say "infinitely" when you mean "very"; otherwise, you'll have no word left when you want to talk about something really infinite. - C. S. Lewis
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Pillar of the Community
Serbia (Srbija)
576 Posts |
Ok thanks guys. So as @Sap said this can only mean that these two coins that I have somehow got "slightly" different composition which resulted in them having different Ferromagnetism, and that can only be done during their minting process, and thus making this "weak magnetic" coin a variant unknown to Numista or KM ?
My collection on Numista page: 7500 different coins and counting... https://en.numista.com/echanges/pro...hp?id=129798 |
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Valued Member
Italy
284 Posts |
Edited by joe_77
11/09/2025 05:35 am
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Valued Member
Italy
284 Posts |
I'll try to recap: Two different macro types of these coins:  Nichel (990/1000) - nice stikes as metal is soft Acmonital (Italian steel) - weak strikes as metal is hard Type 1 of Acmonital, 4 different mixes used: Iron with Cr 19,6% + Ni 10,3% Iron with Cr 16,0% + Ni 11,0% Iron with Cr 19,2% + Ni 9,5% Iron with Cr 20,1% + Ni 9,9% Type 2 of Acmonital (when usage of Ni was impossible due to war efforts): Iron 82% with Cr 18% (traces of Ni of 0,10-0,15%). Quote:
Coins dated 1940-XVIII were initially minted with the acmonital of the first nickel-containing types, then with the new nickel-free alloy; [..] coins were minted with alloys: non-magnetic, weakly magnetic and strongly magnetic. |
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Moderator
United States
188342 Posts |
Quote:
and thus making this "weak magnetic" coin a variant unknown to Numista or KM ? It is not unknown. Numista shows the different versions. Your weak magnetic coin is paramagnetic, I should have been clear about that earlier. I apologize. |
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Pillar of the Community
Serbia (Srbija)
576 Posts |
Ok thanks @joe_77 and @jbuck but I still see the difference from what I have in my hand and whats in the catalogue (talking about Numista and KM)... or I'm missing something ? @joe_77 If I understood you correctly 20c from 1940 should have 3 different versions in terms of magnetism - magnetic, non magnetic and weak magnetic. Maybe my Italian isn't that good (actually its not at all ) but I dont see that in links you provided  First link lists 1940 as magnetic and antimagnetic (or non magnetic), and second link got no 1940 and third link also two versions... Also Numista gives 3 types of this coin: 1. magnetic (with smooth edge) - KM75a 2. magnetic (reeded edge) - KM75b 3. non magnetic (reeded edge) - KM75d But both coins that I have are with reeded edge ! So they are definitely not listed in Numista or KM ! Or this weak magnetic should fall into non magnetic (km#75d) ?  My collection on Numista page: 7500 different coins and counting... https://en.numista.com/echanges/pro...hp?id=129798Edited by mvojnovic
11/11/2025 07:00 am
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Moderator
United States
188342 Posts |
I believe that for practical purposes, the weakly magnetic coin is considered non-magnetic. It appears to me that their goal was to make the coin non-magnetic using the materials they had, which resulted in an imperfect solution.
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Pillar of the Community
Serbia (Srbija)
576 Posts |
@jbuck
Ok thanks for clarifying, sorry if I was annoying :D
My collection on Numista page: 7500 different coins and counting... https://en.numista.com/echanges/pro...hp?id=129798 |
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Moderator
United States
188342 Posts |
No, you are not annoying! We learn by asking questions, even if that means asking more questions when something is not entirely understood or explained. I take some of the blame here.  |
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Valued Member
Italy
284 Posts |
Hello mvojnovic! The info I extracted and put in text is from our main national coin catalogue ( https://catalogogigante.it/). It's hidden in the notes down below in those two pages -- you need to expand the "Note tipologia" part. It is rather confusing so I tried to summarise and hopefully I got it right  In general, I'd rely on our national catalogue rather than Numista. Numista even writes on one of the page that "[..] these coins with smooth edge are not present in official Italian catalogues, so may be very worn coins, defects due to wear of the punches, or, more likely, are fake coins". I am not an expert on these imperial coins so you might want to ask on lamoneta.it (there's also an english section or simply use one of the two "Regno d'Italia" sections)  Edited by joe_77
11/14/2025 11:57 am
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Pillar of the Community
Serbia (Srbija)
576 Posts |
Thanks again guys :)
I think that I wont be going deeper into Italian variations any time soon for my collection, so for now ill keep those two coins as an interesting curiosity :)
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Replies: 16 / Views: 1,291 |
Posted 11/06/2025 3:20 pm
