In Amy Poehler's feminist new netflix film 'Moxie' she has a key around her neck in many of the scenes. There's no explanation for they key during the movie and I'm not saying it's a chastity key- but it's easy to imagine a purpose.
Noticed it too. Also know that it's impossible to go into any store that sells any jewelry without seeing key necklaces! Even Marshall's!
The key necklace is, for many, a "key to my/his heart" connotation, and not necessarily one of locking up genitals.
I'd say any key being related to chastity play is few and far between. Unfortunately, our interest is still limited in scope among general public.
Looks like a house key. edit - The forum keeps changing my link to the exact time. It's at 1:02 in the trailer: