Error Showcase: Jefferson Nickel two-headed off center brockage mint strike error

There's an old saying that when things go wrong they go wrong in bunches.  Exhibit (a) is the multiple error coin pictured below.  Both sides were struck off center because the planchet was not coaxially aligned with the striking dies.  The obverse (heads) side was struck by the proper obverse die but the reverse die was capped by a previously struck coin, so an incuse mirror image obverse design was struck on the reverse (tails) side of this coin.  Good luck finding that in the manufacturing work instructions!  In laymen's terms this is a two-headed coin while in numismatic terms it's a brockage strike.

Coin dies have service lives measured in hundreds of thousands of strikes because dies are hardened steel and planchet alloys are softer.  A Jefferson Nickel die cap is too soft to strike planchets of the same material (copper nickel alloy) because both deform at the same rate, producing a short run of brockage coins that rapidly degrade from early stage mirror images to late stage 'uniface' blobs bearing no resemblance to the original design.  The small distinct initials "FS" (designer Felix Schlag) and other features visible in the photos below indicate that this is an early stage brockage.  If you want a detailed brockage, go early or go home!  See this eBay item 162395383455.

Error Showcase: Lincoln Memorial Cent explosive full brockage mint strike error

Here we have a post-1980 copper plated zinc core Lincoln Memorial cent that had a bad day at the office.  Something went horribly wrong as this particular planchet advanced towards the striking press.  A planchet ahead of this one was struck but instead of ejecting it stuck to the obverse die, effectively 'capping' the die.  Subsequent blank planchets were struck by the capped die until the cap disintegrated or was removed.  The temporary run of malformed pieces are known as brockage errors.  The coin pictured below experienced not only a brockage strike but also a retaining collar failure that allowed dramatic radial deformation and copper plating separation from zinc core.  Also, using the v-shaped rim fractures as a clocking reference you can see one more twist - the obverse die cap rotated 90-degrees relative to the opposing reverse die.  See this eBay item 162391434741.