17th Century, Medieval, Renaissance Keys

[SteamEnGIN]

Hi, I'm curious to know more about these. What metal are they likely to be?
They're heavy. The black scraps off to shiny metal underneath.
What indications do you see on the bow & bit?

Keys came from a collector's estate in Southern California.
They were mounted on this red velvet plaque.


First Key = 7"L x 2 1/2" W
Metal plaque says -
"Llave Espanola Siglo XVII
Coleccion Grinling W. Sibbons
Londres"



Spanish to English translation -
Spanish Key Seventeeth Century
Collection Grinling W. Sibbons
London

Looks like 2 mermaids on either side, like you might see at the bow of a ship?


Second Key = 9 1/8"L x 3"W
Metal plaque says -
"Llave del Renacimiento
Museo Medioebo
eRinascimento Roma"


Spanish to English translation -
Renaissance Key
Medieval Museum
Rinascimento, Rome

I'm new to this and just spent an embarrasing amount of time researching for little reward. :)
Do these seem legit?
What's you favorite reference site or book?
Thanks a bunch!
Melanie