It might seem that the coinage of the Second Polish Republic has already been thoroughly researched and documented. It turns out, however, that there is still something new to discover. Until recently (2021), an uncataloged hybrid existed, where dies used to strike the DEEP STANDARD were assembled for minting with a date offset - DOUBLE DATE (as on the Deep Standard
https://onebid.pl/pl/auction/604/lot/498/rrr-5 zlotych-1930-deep-standard-uncataloged ), while the reverse was struck using a die typical for circulating coins. A highly sought-after and desirable numismatic item.