This is an interesting old cast iron / steel key - dating to the early 19th century.
It is one of four very similar keys that I have in my Iconic Edinburgh online store.
It is a very large and substantial key - with a heavy ring.
These are known as Bullring Keys.
It has a number 24 impressed into the metal, as photographed
The overall length is about 5 1/4 inches. The diameter of the ring is 1 3/4 inches.
It is in good antique condition with no damages.
A nice display item for a period property.