Ok, here's another theory. The Mint was originally going to change to the OH bronze design in 1893 along with other metals, but it was too big a job so they deferred it for 2 years. However, before they abandoned the idea completely, they decided to fulfil the need for 1893 pennies (like 1895 YH farthings, they would be the last of the design) by reusing 1892 bun dies. Then, during 1892-3, they decided all bronze would be pushed to 1895, so suddenly there was a need for 1893 bun head dies, which got produced for the remaining 1893 penny requirement. According to that theory, the 1893/2 dies were used FIRST, but how many were issued is unknown. Quite a lot would be my guess, and not detected before because they are so hard to see.