Wow! I've been collecting these note for years and I never noticed the signature vs. series overlap! Even after reading the great links, it still doesn't make 100% sense to me.
Ohhh yes, I remember now. You're right. Fortunately/unfortunately, I do not collect with that kind of focus. That's my favorite banknote series and I've made lots and lots of progress, but I'm still cllecting by signature/star. Wow.
I heard today (from someone who apparently saw it in coin world) that they're coming out with a silver bullion roujnd/dollar that features the Mercury Dime liberty on the obverse. Can't find any pics or news online though.