Please fill me in on why Ancient Coin got Spellthief treatment? For this example, I'll be using top lane and mid lane as examples. Support will be at the end and junglers (Ha!) are impossible to test.
So, the Frostmancy trick was focus on poking the enemy and getting a lot of gold without csing until you completed the quest. This was typically done in top lane and offered more wards and extra gold income (and apparently gave the enemy a bounty).
Then we have Ancient Coin. To get a Gold Coin, you have to let the minions die and have a chance for either a Gold Coin or a Mana Coin to drop. It is down to luck whether a coin drops or not with the exception being a Cannon Minion which guarantees a Gold/Mana coin. The problem?
Missing a Cannon or 3 Melee minions gives less gold than the gold coin and while 3 caster minions would be worth it, if it dropped a mana coin, it's not worth the loss in gold. People say Vladimir's were recently taking Ancient Coin but I fail to see why since it is nowhere near as efficient and unless I'm missing something, I can't see why it was nerfed.
The only reason I assume is for support if the support stays by the tower when the ADC is gone so if a gold coin drops, they can grab it while being double poked but otherwise I fail to see the nerf.