Medieval Coin? Looking For Help (Id: Likely 16th/17th Century 3 Cavalli From Kingdom Of Naples)

I wonder if this could be a cavallo (or similar denomination) from the Kingdom of Naples, 16th-17th century, under the Spanish.

A number of these types used the Jerusalem cross on one side, and a design that had a firesteel and sparks on the other.

This is probably too large, but gives the general idea: https://en.numista.com/catalogue/pieces119340.html

You forgot the Dukes of Lorraine . Their claim also came through the house of Anjou, with whom they inter-married in the early 15th century. It was this line (Lorraine-Anjou) that then passed the claim to the Hapsburgs when Francois of Lorraine married Maria Theresa in 1736. Lorraine coins like this teston of Francois' father, Leopold of Lorraine invoke Jerusalem on both sides (the end of the obverse legend has REX IE for King of Jerusalem; reverse the cross): https://www.acsearch.info/search.html?id=12367243

Heraldry puzzles like this abound with European coins of that era. What I believe to be on the reverse -- a saltire with a firesteel in the center -- comes from the house of Burgundy, which joined with Spain when Mary of Burgundy married Maximilian of Austria in 1477. That design element is present on most of the coins of Spanish Netherlands in the 17th century.

Part of the great fun of collecting!