I picked this coin up on the Savoca Blue 168 lot 1303. It was only 13euro and I was already paying shipping, so I could not control my button finger. It is pretty much a duplicate of denarius RIC 337 but it is not silver. 17mm, 2.18g. Obv: IMP CAES NER TRAIANO OPTIMO AVG GER DAC Rev: PM TR P COS VI PP SPQR (i think)
It seems like there are occasional "Limes Denarii" as early as Trajan: https://www.acsearch.info/search.html?term="limes+denarius"+trajan (Most seem to be from the Severan period, at least in my experience. I have a couple dozen or so.) If you're not already familiar, Limes ("Lee-Mace") Denarii may have been a kind of token coinage struck in border regions (the Limes) where it was impractical or unsafe to deliver silver. (There are other theories.) https://www.forumancientcoins.com/numiswiki/view.asp?key=Limes denarius https://www.forumancientcoins.com/numiswiki/view.asp?key=Limes Some of mine below. My favorite thing about them are all the different colors of the surfaces (not a great picture, but many of mine are actually very vivid like the OP Trajan) Here's a single photo of the Macrinus from Agora:
