Chamber pot (thunder pot) -- 3 piece

Chamber pot (or thunder pot):  It includes a lid plus a "silencer" as a middle piece that was described by the previous owner as being to quiet the sound when someone used it for its intended purpose (okay, there's no delicate way to say it -- when someone urinates into it).  The bridge piece over the opening in the silencer is about half an inch high in the center.

I couldn't find any date, name or other identifying mark on it.  As the pictures show, it is mostly yellow with yellow flowers on it and slightly raised decorations.  It has a single handle. It's in great shape.  I didn't know what it was when I saw it; I thought it was a really nice storage crock or a serving dish (it's a gross thought now).  I don't know how old this is.

The main thing I'm interested in learning is:  Has anyone seen or heard of a ceramic middle silencer piece in any chamber pot?  Was it common (or is it even true)?  

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