Not all bottles carry “Grand Cru” or “Premier Cru” mention.
For “Grand Cru”, 100% of the grapes used for the cuvee have to be from plots classified “Grand Cru”.
“Premier Cru” can be indicated when 100% of the grapes included in the blend comes from plots classified “Premier Cru”, or if it is a cuvee of grapes from plots “Grand Cru” and “Premier Cru”.
In all other cases, nothing is mentioned.
Keep in mind, champagne has 319 “Crus” --- 17 classified “Grand Cru”, 42 “Premier Cru” and 260 without distinction.
According to Josh Raynolds from Vinous Media, Champagne Brut Blanc de Blancs Premier Cru is light yellow. There are fresh citrus fruits, minerals and green almond on the floral-accented nose and in the mouth. Silky and broad, with strong spicy lift and cut on the mineral-suffused finish. Shows an excellent blend of richness and vivacity, making it very flexible at the table.