Laura’s mystery tile-in bathroom receptor holder thingy — what is it?

What is this mystery tiled-in bathroom receptor? Laura is stumped, and so am I. Do we have any experts out there who know for sure? 

Laura writes:

Hi!

I’ve lived in my 1920’s apartment 20 years and have periodically researched this thing in the wall, which I assume would be a toilet paper holder, but have not been able to find one similar online. 

I’d love to locate a piece that would work with it. Help appreciated! Laura

Wow, thanks! I can imagine the type of device that would go in but haven’t been able to locate anything. 

Laura followed up and clarified that inside, there’s about an allowance of about 1.5” on either side.

Inside a a 1920s apartment bathroom… the way it’s tile it, it looks original to me. What could this be?