I only have Strategic Command: World At War and Strategic Command: European Theater from the series - none have Matrix keys.

The only games in my collection I can think of that have store keys provided for are Battletech and Tales of Maj'Eyal.

Those keys were a Battlefront "feature." It was a BS deal where you had to either buy the game again if had to reinstall the game, or beg Battlefront for a new key for a game you paid for. I flat out refused to beg. Battlefront rightfully went out of business (image that, scum company can't keep jerking people around). The key thing is a thing of the past, though Slitherine is a scum company so it may make a comeback.