So I have a bank here in town that has a few boxes of halves, but I don't make much, so I could only afford 3 rolls for the time being. Bunch if bicentennials, nothing from 1970 or earlier, etc.. so nothing special..then this was the last coin.
Took it in to a PGCS registered coin guy in my area. He did say it was a mint error strike through which was probably grease. My first thought was somebody screwing around with solder, etc.. but he pointed out how smooth it blends into everything it's not soldering or punch/hammer etc. He was able to angle it and get a "shadow" of a 7 in that mess and the tip of a 4. What seperated it from a 1 and a 4 is the placement of the D is lower on the 74's than the 71's.