Interesting obverse brockage - antoninianus of Tetricus I (270-273 AD), Gallo-Roman Empire

[IMP C TETRICVS] P F AVG, radiate bust right // Blank, crude incuse. 16mm, 2.71 grams. 

Very interesting error coin - obverse brockage, created when a coin was stuck on a reverse die, and the next coin was struck with a normal obverse die and the obverse of the coin stuck on the reverse die. Very interesting and unusual.