Silver Eagles on Sigma Metalytics Pro

[SilverLogic]

Hello all, new member.

Anyways let's get into my discussion/questions. Has anybody else noticed the inconsistent testing of a silver eagle when using the Sigma Pro. Many of my Eagles show up in the yellow which indicates caution and to use the measuring feature to further verify. The coins check out after measuring but I was wondering how the purity on one of these coins would look with a more advanced device? I went to the Sigma site and they have links to their unlisted youtube videos which offer different demonstrations on how to use the device, one of those videos titled "Working with Questionable Samples" is basically a demonstration on using the measurement tool when you get one of these inconsistent readings and interestingly the sample silver they use is in fact a Silver Eagle. The guy doing the video comments that Eagles are notorious poor alloys. What does this mean exactly? I have done tons of searches and cannot find any information on what he is referring to nor can I find any other example of somebody saying this is an issue when checking Eagles on the Sigma Pro despite it being the most popular silver coin. I find this sort of strange that there seems to be a complete absence of information on this subject and figured I'd open a dialogue to see if anyone has any insights. Does this mean a .999 fine coin could be more like .997 or .988 ect ect.? I found it kind of surprising and would love to know what others think and if anyone tests Eagles with those expensive scanners I believe they're called XRF what kind of results they give. TIA

[BackyardBullion]

From my best understanding a sigma machine works best on a completely flat surface. This is partly why I don't think they are the infallible testing machine that a lot of people think they are. 

A non flat surface like a coin with definition as pronounced even as an eagle is probably the more likely culprit. 

I have personally melted down a couple of hundred US eagles from mixed dates and when the subsequent bars were assay tested by the Edinburgh Assay Office (which included drill samples and lab testing) all showed 9997 grade silver - so very high and well above the 999 threshold. 

Of course, this is a very small representative sample of the bigger picture but I would think that if the US Mint was consistently putting out silver coins that were less than 999 pure that someone somewhere would have pulled them up on it and made a big deal. 

XRF scanners are a great tool - but they are NOT a good tool for distinguishing 999 silver from 998 silver. Part of the reason I have not sprung $1000 to import one from the USA!

[Chronix]

XRFs scan only surface, sigmas goes a bit deeper as I understand. 
Had couple of eagles tested and they showed green-ish on sigma but weird thing is they showed 31.25-ish grams. 
anyone else got that?

[BackyardBullion]

54 minutes ago, Chronix said:

XRFs scan only surface, sigmas goes a bit deeper as I understand. 
Had couple of eagles tested and they showed green-ish on sigma but weird thing is they showed 31.25-ish grams. 
anyone else got that?

All silver coins will be more than 31.104 ozt because there is always a tolerance built into the manufacturing process. 

Some mints are much more strict on the amount they let go over but in general most mints won't give you less than 31.15 grams. 

Really interestingly the weight you get will be very different to the weight someone else gets if they are at a different latitude. It can swing quite considerably from high in the northern hemisphere to the equator - it is the centrifugal forces from the rotation of the earth that make things weigh less on the equator. So, most mints play on the safe side and go a little over. 

I had a batch of Nuie Owls once, every single one out of a batch of 100 was 31.19 or more. Over 100 oz's we ended up with close to 10 grams of free silver.