I personally categorize coins which are listed as having very small or trace amounts of silver as being AE rather than billion, because they are virtually indistinguishable, at least to the naked eye.
A poster here previously suggested I was the only person who regarded these silver-washed late Roman bronzes as bronzes instead of
billon. Glad to hear that someone else feels this way. <g>
When I responded to this dealer by pointing to a statement about
Roman coins in the Encyclopedia Britannica (XI edition), he changed
his previous post, which made my response to him sound nonsensical. So I then
had to change my post, removing the Encyclopedia Britannica quote. So, here it is: "When the base silver coins are replaced by copper washed with silver the term
billon becomes inappropriate." Many others, of course, describe these coins as bronze coins rather than as
billon coins.
There's lots of interesting misuses of numismatic terms regarding metals and alloys. Along with some people feeling that all
electrum is naturally occurring and bronze coins with virtually no silver in them are
billon, the term
potin is misused or confused too. As Jaimelai pointed out,
billon and
potin aren't synonymous. Some use these terms this way, but I believe this is mistaken or at best confusing.
Tony Clayton, I believe, got this right at
his page. He defines
potin as "an ancient
alloy of copper, zinc, lead and tin... Unlike
billon, it normally contains no silver." He then says, however, that "some alloys containing silver have also been called
potin, such as some from Egypt in the 1st to 3rd century A.D.," but he doesn't say explicitly that this is a misuse, that these coins are better referred to as
billon coins, not
potin coins. I believe that
billon is the better term for these coins,
billon being debased silver, with silver being the more important variable than lead.
Then there are the "golden" dollars (golden colored, maybe). And the silver-plated base metal replicas of
Morgan dollars that are advertised without using the words "
plated" or "
replica," so that some people feel they're solid-silver authentic coins. The list goes on, or could.