This is a 100A 125/250V female connector designed for use at the end of a dockside shore power adapter or extension cord. Typically, such an adapter or extension cord would be custom built from components.
This connector has a weatherproof cover for those times when the extension cord may be left on the dock while your vessel is away, or simply to keep the contacts clean and dry when the cord or adapter is not in use.
The dock end male plug on your 100A 125/250V cordset mates with this connector.

Yellow Zytel, a super tough nylon, watertight connector body
Spring-loaded cover closes automatically when not in use, and is watertight (IP67 - withstands temporary immersion) when securely fastened
Cord grip range is 1.00" - 1.94" (25.4 - 49.3 mm)

NOTE: This device cannot be mated to a boatside shore power inlet. You must use your cordset, with its M4100C12R female connector to connect to your vessel's shore power inlet.