This page attempts to summarize all information on the Internet about lead-filled 100 ounce silver bars, as well as provide some new thoughts and insight. NOTE: We are actively seeking one of each type of lead-filled silver bar to run tests on, but have been unable to do so. Please if you have one you would sell us or let us borrow. Thank you!
We also have a page on the pure lead fake Engelhard 100 ounce silver bars.
Over time, pictures of 2 different lead-filled 100 ounce bars have surfaced on the Internet. The picture on the left, posted in 2003, is from a 100 ounce silver bar from 'the 1980 silver bull market'. The picture shows half of the bar, which had been cut in half to verify that there was lead in it. You can clearly see 3 holes that had been drilled into the bar. The pictures on the right show bars that were hollowed out, and then filled with lead (or lead/tin slugs per one source).
The description of the bar on the right (hollowed out) also states that the weight was exact, and that it was polished smooth (presumably nearly indistinguishable from a real bar).
Some sources say that they are virtually indistinguishable. Someone claiming to have been in the precious metals refining business for 40 years said " In each case, this plug was on the end of the bar and could be seen by careful examination. They ground it down flush but you could still see it."
New information: According to the FBI, they showed Engelhard and U.S. Mint employees samples of the Type II (hollowed out) bars, and they were not able to identify them as adulterated.
Finally, the bar is smoothed/polished and weighed, to both look as much like the original bar as possible (hiding any evidence of tampering), and keeping the weight as close to exactly 100 ounces as possible.
Then, the person doing this would need to find a way to sell the bars, and find a buyer for the silver shavings as well.
For more details, you can check out our page on Type II Bars.
Another person who claims to have worked many years in the refining business says that he has only seen 2-3 lead filled 100 ounce bars out of 1000s that he was involved with.
In the FBI Case, it was claimed that about 150-200 bars were created (of which 16 were recovered), meaning that at least 150 or so such bars made it into circulation (and as many as 500 or so, per our calculations, based on their purchases of lead). Common sense dictates that it is likely that several people did this on a similar scale, so perhaps 1,000 or so bars made it out there (likely many of which have since been discovered). That would be about .05% of all Engelhard 100 ounce bars being tainted, or a 1 in 2,000 chance of having one.
Another point: major online bullion dealers do not place much emphasis on lead-filled 100 ounce silver bars. If they were as prevalent as some suggest (1:25 to 1:40), they would have lots and lots of customers sending in bogus bars (many send in 10+ at a time). Those customers would certainly start complaining, but there aren't any complaints of anyone sending 100 ounce silver bars to major online dealers that told them that they were filled with lead. This makes the ~1:2,000 estimate seem more accurate.
So if it used a tin-lead alloy, it would likely be exactly 80% lead and 20% tin.
However, one person claims that the bars he saw were filled with pure lead. And, the "Type II" hollowed-out bars appear to have been made from pure lead (based on receipts we have copies of, and no information suggesting an alloy).
Although both silver and lead are diamagnetic, the level of diamagnetism is slightly different. Therefore, it may be possible to detect a lead-filled silver bar either with a strong magnet, or if not, with a Magnetic Susceptibility Meter. Magnetic Susceptibility Meters cost about US$3,000 at this time. It is not known for certain if these would detect lead-filled silver bars.
If you have a strong magnet, and place a 100 ounce silver bar at a 45 degree angle, the magnet should slide slowly down the bar (much slower than it would on, say, a book at a 45 degree angle). In the 3-drilled-holes type of lead-filled silver bar, it's possible that you would notice a change in the speed if you did this (with the bar sideways, so the magnet would go down the short side of the bar, not the long side).
For the curious, the molar susceptibility of lead is -23, silver is -19.5, and tin is -37.4. An 80% lead and 20% tin alloy, if it has the same magnetic properties in proportion to the amounts of each metal, would have a molar susceptibility of -25.9, about 30% more than silver.
However, be aware that the ring test doesn't always work for real silver! For example, a 100 ounce J&M silver bar was cut in half (by silverstockreport.com) because it didn't pass the ring test, but it turned out to be pure silver.
In theory, an ultrasonic thickness gauge should detect the lead-filled silver bars. Sound travels at different velocities through different materials, and echoes when it hits a different material. In normal usage, an ultrasonic thickness gauge would be used to measure the thickness of a silver bar. If sound travels through silver at 1 inch per second, and it takes 2 seconds for an echo to come back on a silver bar, the bar is 1" thick (since the sound goes through the silver from the top to the bottom, and then the echo goes from the bottom to the top, so the sound travels 2" if the silver bar is 1" thick).
Ultrasonic thickness gauges are usually used to determine the thickness of something you have access to only one side of (such as the metal wall of an oil tank). But here, we have access to all sides of the silver bar, and therefore we already know the thickness of it (about 27mm, or 1 1/16").
So, when calibrated for silver, you would place the probe (transducer) of the ultrasonic thickness gauge on the silver bar, and if it is real silver, the ultrasonic thickness gauge should show the thickness as about 27mm (perhaps around 25-29mm, accounting for a high error level, in case the bar is slightly thicker or narrower than normal; the gauges are typically accurate to .01mm if calibrated properly).
Sound travels through silver at 3600 meters/second, and through lead at 2200 meters/second. That means that sound travels about 40% slower through lead than silver. So if you measured a 27mm thick lead bar, and the gauge was calibrated for silver, it would show up as being 63% thicker (3600/2200), or 44mm. The doctored bars aren't pure lead, though.
If you have a lead-filled silver bar, our thoughts are that one of the following would occur (from most likely to least likely):
Note that an 80% lead 20% tin alloy would handle sound differently; sound travels through lead at 3300 meters/second. If sound travels through the alloy proportionately to the amount of each material, that would mean sound would travel through the alloy at 2,420 meters/second (3300 minus 2200 is 1,100 times 20% tin is 220 plus lead's 2200 is 2,420). That's 33% slower than silver, with 1" of lead measuring as 1.36" of silver. In that case, numbers for the last two scenarios about would be different (34mm and 30mm). That is still 10% thicker than the bar actually is.
Also, at some points in the bar, the thickness would be 100% silver. So you would need to be sure to measure where the lead is, at its maximum thickness. If taking just one measurement, doing so at the exact center of the bar would get the maximum lead thickness for the two types of bars in the pictures at the top of the page.