dominion icon

From what I can tell by the announcement, you had to have the 100 wins before the announcement; but I'll be on the lookout for clarification, and you can always submit a ticket for clarification from Player Support as well.

For players who’ve made the Crystal Scar their home over the last four years, we’ll be taking a snapshot of the queue today just before this post goes live. Then we’ll give out an exclusive, never-to-be-reproduced Summoner Icon to anyone with over 100 wins in matchmade Dominion games (not including Co-op vs AI).

http://na.leagueoflegends.com/en/news/game-updates/features/retiring-dominion

As stated in the announcement, the cutoff was basically right before the announcement was posted. So you had to already have 100+ wins. They probably did this to cut down on people flooding the mode just to try to get the icon over the next week. It keeps the icon a truly special thing for people who really were more dedicated players of that mode.

[slayer-pantheon-popcorn]

that's annoying, I played the game mode often considering I've only played league for this past season, it's not fair that I can't try to get a few more wins for it :\