I noticed this while looking through the 1981 Donruss set last week. Three different teams are wearing black armbands.
Can you name the person each team was honoring?
Up first are the Chicago Cubs. This card of Rick Reuschel shows the thick black armband on the left sleeve. It's a little hard to make out because of the darkness of the card, but trust me, that is a black armband.
The Atlanta Braves also are wearing them. Here we see the black armband on Sarge's left sleeve.
And finally, the Yankees are wearing a narrower armband on their left sleeve, as you can see on Eric Solderholm's card.
One of these is pretty easy, one is not too hard, and one would be known mostly to die-hard fans of the team. Leave your guesses in the comments and I'll check from time to time to see it the correct answers have been given.