NotCot has an potted history of champagne glasses here. About the coupe they note;
Then appears the “coupe” (or glass) at the beginning of the 1830s, a new glass first used during buffets because of its easy using for caterers and waiters. The “coupe” has a different appeal from one culture to another: it is elegant for British people and is popular in Russia because of its ability to contain more champagne...