My thoughts, for what they are worth:
The core combo appears to be Mint/Warehouse/+$2 action. The goal is to use Warehouse to line up a 4-card hand of three Coppers and your +$2 action, so you can buy Mint to good use (trashing 3 Coppers a pop) without having to wait for a lucky 5-Copper hand and without having to give up a Silver. Do this twice and you are good to go.
Duchess worked here because you happened to have a $2 hand early, but any other cheap action source of +$2 would also work. Perhaps the optimal 4/3 opening for this strategy on this board was Warehouse/Fortune Teller.
The Islands were helpful sifting, but you could probably have still made the combo work without them - just buy an extra Warehouse instead.
Ultimately, you're running something akin to Chapel/BM, but with built-in sifting and treasure gaining that happens concurrent with your greening. And so is less apt to choke endgame (but again, a single Warehouse by itself probably isn't enough sifting late-game).