Hi Jeff -- Very nice. Let's see a picture of the cannonball!!!
The coins are 4 reales (the denomination) silver coins from Mexico, when Mexico was a colony of Spain. The inscription says CAROLVS ET IOANA, that is, Charles and Joanna, who ruled Spain in the early 1500s. If your coins are genuine, that's when they were minted.
The coin my picture is in beautiful condition. It sold for $750 US dollars. Yours should have a similar selling price to a collector (not to a coin dealer), or maybe a little less because your coin does not have the eye appeal of the pictured coin.
The main concern is authenticity. If your coin is genuine, it is worth hundreds of dollars. If it is a reproduction, it is worth a few dollars.
Take your coins to a jeweler and have them tested (non-destructively) for silver content. If not silver, they are not real.
Next, get a precise weight for your coins. Genuine 4 reales weigh about 13.5 grams, plus or minus 0.2 grams. If any other weight, they are fakes.
Here is the auction description of the coin in my picture (CoinQuest thanks Daniel Sedwick for use of his coin photo):
Daniel Frank Sedwick, LLC > Treasure Auction 31 Auction date: 4 May 2022
Lot number: 413Price realized: 750 USD (Approx. 711 EUR / 600 GBP / 737 CHF)
Mexico City, Mexico, 4 reales, Charles-Joanna, "Late Series," assayer G to right, mintmark M to left (M-G), NGC AU 53, ex-Lawson (stated on label). Nesmith-50c type; Cal-127; S-M5; KM-18. 13.63 grams. Lovely example struck on an impressively broad flan with contrasting toning rendering legends and details sharp, capped by an unusual shield-side legend-ending of three o's. NGC #6448110-025. Pedigreed to the Clyde Hubbard Collection of Mexican Charles-Joanna Coinage and to the Lawson Collection (Superior Auction of June 1985, with original lot-tag 2837). Accompanied by original tag or holder from Clyde Hubbard. ($700-1000)