This "Custom Made Roman Constantius II Bronze Coin Bracelet" is for sale on eBay. It is not Constantius II but Maximianus though. The real question is why would anyone put a worn coin worth at most a few dollars into a 14k white gold watch band (with what looks like diamond chips) that they are trying to sell for almost $1300.00!
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It does come with a certificate of authenticity, but the COA shows a different coin that actually is Constantius II.
"Roman Constantius II Bronze Coin Bracelet
14k white gold watch converted into bracelet. 13mm width. Dia: 42-1mm. 7.5" wrist. Weight: 41.7g.
Coin: Constantius II, bronze, 37-361AD, cert of authenticity.
Just marked down from $1995!!"