This is probably the coolest thing I've ever owned...
Forger’s reverse die of sestertius
mid 2nd century AD – AE or PB? 53.5g, 35x6mm
four-tiered pyre topped by facing quadriga
CONSECRATIO, SC in retrograde
type of RIC 315, 1266 (Antoninus Pius); 333, 1511 (Lucius Verus); 441, 662 (Marcus Aurelius)
ex Dmitry Markov New York Sale XI, unsold
When a counterfeiter prepared his dies, he could either engrave them himself, in a style easily be distinguishable from official mint issues, or he could use a genuine, mint issued host coin. He would then impress this design into a piece of bronze and affix it to the iron die-shaft. This object likely represents a counterfeiter’s first attempt, a practice strike in lead.