Many of us like to buy special wines for the Pesach sedarim. This year is a Hakhel year, which means we have to be extra careful to avoid purchasing wines from last year (Shmitta). Many wines that usually carry a kosher symbol will not have a symbol on wines from 5775, and some may have a supervision that relies on leniencies not accepted by all.
The OK certifies 33 wineries in Israel alone! These wineries have over 500 labels of wine and more than 150 mashgichim between them. The OK strictly monitors all certified wineries, even during Shmitta to ensure that Shmitta wine does not carry the OK symbol.
The labels on Shmitta wine look exactly the same, so double check for the kosher symbol before you buy.