This hints at why I only do junk silver.
One can google “chinese gold” and find sites that advertize fake gold bars. They actually have a pretty thick gold coating. The idea is that they are great “sales contest” prizes.
They are tungsten filled and, apparently, tungsten and Gold weigh pretty closely the same.
Tungsten and gold weigh “scary” the same (very very close)
But silver is not immune. Pewter (and there a hundred different alloy compositions of pewter possible) in a fairly precise proportion can weigh and specific gravity out just like silver. It of course will not ring like silver and will not act like silver when brought near a neodymium magnet.
As you say, junk silver is IMO a reasoned choice as it is “self-assaying” as long as you stay clear of silver dollars, which are getting to be very widely counterfeited. For the moment, nobody thinks it would be worth it to counterfeit a 1959 quarter. That means sooner or later, you’ll be able to count on it happening.