I presume this irregularly-shaped, raised thing behind Pietas's head has resulted from a die break. Could it be anything other than a cud? Let's see your coins with die-deterioration or anything else you feel is relevant! Trebonianus Gallus, AD 251-253. Roman AR Antoninianus, 3.69 g, 20.2 mm, 7 h. Uncertain mint, AD 252-253. Obv: IMP C C VIB TREB GALLVS AVG, radiate, draped and cuirassed bust, right. Rev: PIETAS AVGG, Pietas standing left and raising both hands; altar at feet. Refs: RIC 72; Cohen 88; RCV 9643; ERIC II 41.
Here's one with a die break on the emperor's ear. Elagabalus. AR denarius, Rome, 219–20 CE; 19mm, 3.65g. BMCRE 158–60, RIC 130, RSC 244. Obv: IMP ANTONINVS AVG; laureate and draped bust r. Rx: PROVID DEORVM; Providentia standing front, head l., leaning against column, legs crossed, holding wand over globe at her feet and cornucopia. Near EF.
The chunk next to the turtle on this Aigina stater is a cud. Gordian III in reverse right field closer Septimius Severus cud obverse at 1 o'clock on the V Syracuse tetradrachm has die failure behind the head of Arathusa. This specimen was struck unevenly, I believe, intentionally to lessen pressure on the break hoping to allow the die to last until its replacement was finished. Coins of this die are known with several different degrees of this failure.
Die break... contagious enough to infect the reverse... Etruria Populonia AR 10 Asses 20mm 4.21g 211-206 BC Obv: Male Hd Rev: Blank die break
Not a cud, but a strike error instead. Constantius II AE2 double struck portrait. Pretty worn, but interesting D/S placement, like 2 emperors side by side.
Spot the die cud(s?) on this very busy obverse. CILICIA, Tarsos Tarkumuwa (Datames), Satrap of Cilicia and Cappadocia. AR Stater. 10.7g, 24.5mm. CILICIA, Tarsos, circa 375 BC. SNG Levante 85 (this coin); Casabonne Type 2; Moysey Issue 6; SNG France 282 = de Luynes 2839 = Traité II 609. O: Baaltars seated right, torso facing, holding grain ear, grape-bunch, and eagle-tipped scepter; lotus below throne; all within crenelated wall. R: Satrap, wearing Persian dress, seated right, holding arrow; winged solar disk to upper right, bow to lower right; c/m: bull standing right within incuse square. Ex CNG 100 (7 October 2015), lot 1553; Ex CNG 96 (14 May 2014), lot 516; Ex Eduardo Levante Collection (CNG 64, 24 September 2003), lot 337.
Die Break... I have seen this on other other ones of this issue... but it is cool and makes her a little meaner looking! Etruria Populonia 3rd C BCE AR 20 As 8.1g Metus Blank HN152 I think @Ed Snible has a really cool one with a similar (same?) die break... his coin’s patina is really great.