Fake or not? Whats missing?

[Silverman2U]

Ok so may need a bit of help to understand if I am missing something here. All other tests other than XRF (not done) come back clear/good. Ping test, weight, diameter, thickness, detailing on side of coin, signs of wearing in keeping with ages of coin.…. 
 

But the sigma pro mini sends them into the red when do the conductivity test. I tried out a bunch of my other crowns no issues all in green. 

Those 3 crowns look very real so I am rather perplexed. 🤔 

@James32 @BackyardBullion @Fadeingstar or anyone that has a sigma pro mini would appreciate thoughts and input. 

NOTE: After entering the weight of the coin and testing dimensions this was within acceptable limits, just that conductivity that was out of sync, and only on 3 coins?!  

Edited July 21 by Silverman2U
Update

[James32]

I've only the original unfortunately. 

 

[BackyardBullion]

Really hard to say without seeing the coin.

Have you done a specific gravity test?

The only other tests available would be an acid test (destructive) and take it to a dealer and have them check it over. 

The only thing I can think of is that the database of coins that the sigma is based off doesn't have that coin in it and therefore the results are skewed. 

Sorry I cannot be more helpful!

[Silverman2U]

1 hour ago, BackyardBullion said:

Really hard to say without seeing the coin.

Have you done a specific gravity test?

The only other tests available would be an acid test (destructive) and take it to a dealer and have them check it over. 

The only thing I can think of is that the database of coins that the sigma is based off doesn't have that coin in it and therefore the results are skewed. 

Sorry I cannot be more helpful!

Yes thanks was my thoughts at moment too.

May just give sigma a call too. 

Just now, Silverman2U said:

Yes thanks was my thoughts at moment too.

May just give sigma a call too. 

Not done SG test, easy enough to do on these old coins. That’s up next.  

[CollectForFun]

19 hours ago, Silverman2U said:

just that conductivity that was out of sync, and only on 3 coins?!  

Well, those test results seem to be way off, unfortunately... (especially the latter two which are completely out of the range). Only XRF test or at least standard Sigma test, if successful, can dispel doubts at this stage I'm afraid.

[paulmerton]

I have analysed many old crowns on sigma devices and I would not be overly alarmed at this at all, as long as everything else checks out.

The sterling silver setting is looking for something that is 92.5% silver and 7.5% copper.

The problem with genuine 100+ year old crowns is that the 7.5% non-silver component usually contains additional metals beyond copper, and while the amount of silver is fairly consistent, the proportion of the other metals (call them impurities if you prefer) is not very consistent and is enough to throw the readings out of range - usually off to the right of the scale.

Ultimately, sigma testers pretty useless for testing old crowns because the alloy varies so much.

[CollectForFun]

BTW, haven't you tried testing those coins with some of the other silver settings than just sterling?

[paulmerton]

16 minutes ago, CollectForFun said:

BTW, haven't you tried testing those coins with some of the other silver settings than just sterling?

I don't think there would be any merit in doing that. Hunting around for an alloy it appears to match won't mean it's made of that alloy.