Classic Commendation

Classic Commendations are an elder game commendation that can be earned from flashpoint and operation bosses and by completing level 50 Group Finder and repeatable missions. They can be used to purchase specialty items from Classic commendation vendors. Classic Commendations have a max limit of 1000.

Source
Classic Commendations are mission rewards that can be obtained from any mode operation bosses in The Eternity Vault, Karagga's Palace and Explosive Conflict. They can also be obtained from level 50 group finder and repeatable missions.
 * Mission reward

Conversion of commendations
With the Rise of the Hutt Cartel expansion, Daily, Tionese, Columi, and Black Hole Commendations were converted to Classic Commendations. Below is the rate of conversion for existing commendations:
 * Tionese Commendations - 6:1
 * Columi Commendations - 4:1
 * Daily Commendations - 4:1
 * Black Hole Commendations - 1:1

Missions and loot that previously awarded the above commendations will now award Classic Commendations instead.