I wasn't sure what to call this - "peephole" seems more like a small round aperture. Not that this need have any function - it just needs to look the part. The slot that opens on the door of speakeasies or gambling dens in old movies, through which the doorman rasps: "What's da passwoid?" Could even be designed as a jail cell door. I couldn't readily find any photos on the internet, so I've attached a drawing I did for one of my students long ago.

I'm not sure where you can find one, but I absolutely love how vivid your description of the doorman was. The drawing is really nice too.