While picking up coins in exchange for another fake I noticed a Roman bronze of Gratian that seems to have kind of 2 heads on obverse. It could be some sort of double strike or even clash. In fact I'm less than a beginner in coin errors. The coin was struck in Aquilea and weighs 3.77 g. RIC 30 a. Is it really an error? Are errors scarce in ancient coins?
Double and overstrikes are common in some eras. In fact, I dare you to find a NON-error of certain Byzantine emperors. As a general rule, ancient collectors usually like nice coins. Not many ancient errors are collected on purpose except maybe double headed coins.
There are two levels of 'error'. Sloppy workmanship is not so much an error and not collectible by me until it gets really sloppy or shows something interesting about the way coins were made. When an oddity crosses over into the weird, there are some of us who love them. I would truly love, love, love to find a coin like the overstrike below in smooth, attractive condition. The left side of the obverse was a die of Constantius II while the right came from a die of Constantius Gallus Caesar. As a result, we see what appears to be a coin with wreathed head portrait that reads NOB CAES. Both reverses were falling horsemen. I really hoped I had something here for about thirty seconds until I realized it was just an overstrike and worth no more than the $5 I paid.