Funny Ebay Listing!

I think it is a Limes denarius, a denarius minted from bronze.

It is a limes denarius, often called an AE denarius. If you want to see more, visit my pages:
http://augustusmath.hypermart.net/Imitation.html
and
http://augustusmath.hypermart.net/imitations3.html

"AE" is a nice catchall designation for base metal coins that are mostly copper. Some are virtually all copper (e.g. AE From Valentinian) and some have enough tin to be called "bronze" (although modern bronze has more tin than almost all "bronze" ancient coins) and others have enough zinc to be called "brass" (= orichalcum), which is somewhat yellow (looking a bit like gold made it more valuable. The brass lamp in front of me now looks a lot like gold). Cope, Padfield, and others have done chemical analyses and the results are quite irregular, varying even in one reign from one mint to another.
If it is a yellow sestertius, you can call it brass if you want. Some of the coins said to be "bronze" really have tin in them (often 5% or less, compared to modern bronze commonly at 12%). However, many coins often said to be "bronze" coins are of undetermined copper alloy, often without much tin. Sometimes "bronze" is just an old and outdated terminology continued to the present day. You can just say "AE" to be safe if you are not sure.