Hi Wilhenry,
I love all the tiny things you have been showing us. We played many hours of cards in my house. Wished I could find somebody who still enjoyed playing. Most people that play seem to use online games.
I am not sure but I think this could have been for either the card games "Bridge or Whist". It would have been used a personal device set on the card table to remember what the "Trump Card" is for the hand. The trump card or suit is a designated suit that has a higher rating and thus beats all the other suits.
PeLady