Vintage Solid Brass Fish - Door Knocker (?)

Vintage Solid Brass Fish - Door Knocker (?)
11 pcs available - but are they door knockers? Please help me to identify.
From top fin to base hole holder it is: 5 1/4 inches high. From the mouth to
the tip end of the fin it is 3 11/16 inches wide & the base is 3 7/16 long
It is 9/16 of an inch wide at the thickest part of the base - What is the missing part?
BE THE FIRST TO IDENTIFY WHAT THIS BRASS FISH IS USED FOR & GIVE THE NAME OF THE MISSING PART AND YOU WILL GET A FREE CHROMOLITHOGRAPH (COLOR PRINT) OF YOUR CHOICE FROM THE ANTIQUE PRINTS GALLERY SHIPPED TO YOU FOR FREE TO ANY PART OF THE WORLD.	BACK

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