Can I discard a duplicate with my Wintertime marauder?

A duplicate is not a unique card?

Text:

Ironborn, Army If it is Summer and you reveal a plot card,kneel Wintertime Marauders. Response: If it is Winter and you win a challenge in which Wintertime Marauders is participating,choose and discard a non-unique card from play.

Core rules (p. 19), as clarified in the FAQ (p. 4):

"Duplicates have no text, titles, traits, or crests."

They may as well be face-down. So, since they are considered to have no title, they cannot be considered unique. And, since they are in-play cards, they qualify for Wintertime Marauders' ability.