I wonder if there was an access panel behind it. Like to a safe or something.
Or a safe room. Those are pretty common now in high end homes in case of intruders.
My favorite is a story I heard about an elderly woman that lived alone had a multipurpose room put in her home when it was remodeled. She had a secure room built that was her safe room but also set up to store her firearms and ammo.
Al Capone’s Vault!
Where’s Jeraldo?