I'm trying to finish up my very last anima weapon (yay!) and I ran Void Ark because it was on my WT, I had a Mhach Farthing stuffed on a retainer, and I wanted a second one to turn in alongside the x5 Allagan Catalyst for Crystal Sand. (The specific quest is "A Dream Fulfilled.")

After completing Void Ark, I did not get a Mhach Farthing. Since it is no longer needed for gear upgrades, I fear it was removed from the game as a potential drop entirely. But it's still available as a turn-in for Ulan's Note, even though there is no way for any new player to ever obtain it, let alone get two of them.

Ulan's Note has been modified and updated in the past, but this may have been an oversight. Or, if you want to continued to allow someone to trade in any old coins, consider including the Mhachi Penny and Mhachi Shilling as an option as well (I've got like.... 30+ of those I never did anything with) or the Rabanastran, Gougan, or Mullandes Coins.