Victorian soil vent pipe grille - tiny key attached??

[Francfalco]

It`s not a key at all - It`s one hinge of the mica flap that hung down inside the cover to act as a Victorian AAV There is a small hole where the other one was fixed

Nige F - thankyou so much! - you've saved my sanity!

Just Googled what a mica flap and AAV are and all makes sense now!

Thanks forum

Have to admit, I'm slightly disappointed it isn't the key to the Borrowers front door