Vintage Coventry Fine Porcelain Electric Clock Base

This a rare, green enameled clock base. 

Typical versions are white with gold gilding.

I am not sure if this one is a one-off, a limited edition, a prototype, or just professionally enameled by someone who likes green. 

There is no readily available history on the piece.

Coventry mark and Made in USA is visible, but model number's letter is not discernible.

Measures approximately 8” x 7 3/4” X 3"

Believed to be manufactured in the early 1950s