Does the Trophy Shop always sell unique trophies?

In "Games & More" > "Vault" > "Trophies" > "Shop" Smash for Wii U contains a shop where you can select from one of eight trophies to buy. This selection of eight is different almost every time you load up the shop.

However, what I'm worried about is buying a duplicate trophy. Does the Shop only ever stock trophies you don't already have? I don't want to accidentally spend a whole ton of money on a trophy I already have, and I also don't want to have to go all the way to my Trophy list in the Vault and check every time before I buy a trophy from the shop. Thanks!