There are 2 versions of the Senigallia Medallion, the only extant portrait of Theodoric that we know for sure. One is the original, a small gold medal not much larger than a thumb, which has a fixture on the verso, to use it as a brooch.

Then there is a copy made in the 1900's for Vittorio Emanuele III, King of Italy. It is identical, but the verso has no brooch support. The copy is usually sent away for exhibitions, and it's what I saw last year at the Saints Bankers Kings exhibition in Ravenna. I did wonder why it had no support in the back.

Actually, both versions are usually kept in the Museo Nazionale in Rome, at Palazzo Massimo, 68 Piazza dei Cinquecento (right in front of Stazione Termini). They can be seen in the lower underground floor, to be precise on the far wall from the entrance, on the left.

You can guess I've been there. :D