The first photo is a 15-amp twist-lock receptacle. (Besides finding replacements on the Internet, it appears to be stamped in the metal mounting hardware on the part.
The second photo is a white reflector. Just guessing; a PO probably added it, perhaps to be able to locate the Airstream or doorway, in the dark. Prior to a 1968
change in Federal Motor Vehicle Safety Standard 108, a lot of vehicles had white turn signals and reflectors on the front.
Regarding the last photo, it's up to you to decide if you want to clean up the original part. If you replace it, I suggest you look at replacement receptacles in a marine parts catalog or online (e.g., West Marine). Marine parts are usually made of stainless steel, and will look nicer and last much longer.