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Baseball did not exist in 1804, and the players that signed the cards would need to be known to give a value.
$5
130
Signed cards can be worth more or less than an unsigned card. Some collectors see signed cards as marked.Cards signed by an individual other than the artist are usually worth less than an unsigned cards, unless that are signed by a person of note from Wizards of the Coast, like Richard Garfield.Signed cards are legal in tournaments per the official DCI Universal Tournament Rules (linked), which state under Rule 28- Taking Notes: Cards used in a tournament may not have writing on their faces other than signatures or artistic modifications.
If they are really rare up to $200
There are many cards claiming to be retirement cards. They range from 10 dollars a card to thousands of dollars a card.
Hotel Laguna by Mayer
If it is signed by him? Possibly a pretty penny. If it is not signed by him? Standard used book price.
A signed Van Gaard 202c painting is worth about $1,250 today. This can fluctuate from day to day, and can also depend on what kind of condition the painting is in.
Unfortunately, I too thought that by now this set of cards might be worth something. It was a Gatorade promotion that produced these cards. If I remember correctly, you had to send the Gatorade proof of purchase to receive the set of cards, which many people did. So these cards are not all that rare. The entire set is only worth $28 dollars.
A signed and number Sehring Lithograph of a boy and a girl in a beach is at least $150.