Often there is a raised number on the housing. Take a photo with your phone and then do a Google search. It should come up with a taillight assembly.
If it needs replacement and it's an automotive lens, you can often find ones that have been converted to built in LED.
If no luck with a number, post a photo and someone might recognize it. My 2014 DS was a Dodge truck.
Don & Mary
2019 Newmar Dutch Star 4018
2019 Ford Raptor