Volvo has not yet even begun the seat heater recall so no one knows. When they do, they will notify customers. If one is still questioning that or has moved, second owner, etc, one can then call a dealer to have them run DCS which will tell them if that car is part of the recall. Don't call until it's started (sometime in January) because they simply won't know, can't.
There's only about 6000 cars in the US getting this recall so not every '95-'96 850 will need it.