the 'cover' can be pinned into place in the 4 corners. What I would call the square recess or socket that is the "mystery" of the item measures approx. 3x3.25in and this is reflected in the medallion shaped base that is not round either.
the decoration is pierced and chased with scrollingleaves and inscribed with IHS XPS (christogram).
I was hoping that one of the members would enlighten me here
![Image](https://preview.ibb.co/ga2m7y/base1.jpg)
![Image](https://preview.ibb.co/go9oLJ/base2.jpg)
![Image](https://preview.ibb.co/kiitny/base3.jpg)
![Image](https://preview.ibb.co/fDQTLJ/base4.jpg)
![Image](https://preview.ibb.co/hJjoLJ/base5.jpg)