Before 1990 (I think), mintmarks were hand-punched onto each and every die. Someone just didn't do the greatest job and slightly rotated the mintmark punch. Worth 3 cents, no additional value
Mintmarks within a series of coinage will vary from date to date, and, more typically, from die to die. Sometimes they are intentionally altered to improve the mintmark's clarity (like hollowing-out a filled mintmark, for example), and sometimes they're tilted, strike-doubled, etc. unintentionally by the inaccuracy of the strike. So, generally speaking, no two mintmarks are completely alike. -Brian
