I'm thinking it was struck more then once... I see faint remnants of letters on the stretched out parts of the reverse.
Full brockage broadstrike. Coin stuck to the obv die, second planchet fed in below it, and the stuck to the lower die when it retracted so it wasn't around the lower planchet to restrain it. Planchet was struck by the capped die. Thre extra material between the dies resulted in much higher pressure than normal, and since the collar was not in place the planchet and the coin on the die expanded outward greatly. On the reverse the expansion resulted in tearing of the copper plating. On the obverse since both pieces expanded togeter the plating didn't tear and the design of the brockage extends all the way out to the edge of the coin evenly without excessive stretching and distortion.
