The obverse of the 1860/59 coins are always seen with the same features highlighted in RED on the attachment, doubled ‘ghosted’ ribbon, and scuffs under this ribbon and QV’s chin. Apart from the date features these things confirm all these pieces were struck from a single altered 1859 die (i.e. the narrow 59 type, which is fairly rare variety in itself on an 1859).
I believe that an average figure for the number of coins which could be struck from a new die was around 30,000, but if a die was already partially used then it would probably produce less than that figure.
I’m just wondering whether the rarity of 1860/59’s could be partially explained by the practice of using dies from earlier years, but not altering dates. For example, I understand that the mint figures for 1848 are only around 160,000, whereas for 1849 they are stated as 268,800. Clearly, however, 1849’s are much rarer than 1848’s, so this suggests that most of the 1849 number of 268,800 actually bear the date of 1848; the mint not bothering to alter 1848 dated dies when the calendar moved to 1849.