Here is my opinion on the matter.
The only true way to tell on a 100 ouncer is to saw it into pieces. Short of that, you can try the "ring" test along the entire bar.
One ounce bars are easy to check with the ring test. I don't believe this is fool proof but I do it anyway if I am unsure.
I am a big fan of silver bars--but for me only 10, 5 and 1 ounce bars from well known refiners. Sometimes I will buy the old "art bars" from the 70s when they are in the cheapo bin at the coin store. Up till now if someone was going to counterfeit it would seem to be more cost efficient to only do 100 and 1000 ouncers.
I think if silver ever does blast past 50 we will start seeing counterfeit silver rounds and bars in all sizes. When I have been in coin stores they never seem to analyze the individual bars much at all when people sell them if they are from a well known refiner. To me some unknown round or bar saying .999 fine silver is not enough to convince me, so I avoid them if I am not familiar them.
This is one reason if you are worried to stick to gov issued rounds, since there would presumably be harsher consequences for counterfeit, although that apparently hasn't stopped the Chinese from making fake old US silver dollars and such from what I have read.
Old US junk silver (circulated dimes, quarters and halves) is probably the best way to avoid getting counterfeit silver bullion. My favorite are not too much circulated Franklins from later years since, unlike Kennedy halves, you don't have to check the date to make sure it is a 90%er.
Jim
