You could flick it and see if it sounds like plastic or not. Whats the instead of the bowl look like? Does it look like its used for smoking?
Because I would think if its for smoking, Clay would make more sense. Can you see any scratched on it? Like where the paint came off or if its solid thru?
Wasnt trying to be rude, its just hard to tell when its physically not in my hand.
One thing you can do is heat up a sewing pin with a match and very lightly touch the tip to an inconspicuous place on the object. If it's plastic, a small indentation will be left where it melts. If it's clay, then obviously it won't. Of course, this method isn't suggested for an object of value, but if it's plastic it may not have a huge value anyway depending on what it is.
From the pictures I do agree that it looks like a pipe bowl which will be made of clay or other heat resistant material. Although the hole for the stem is rather small for a pipe.
This pin method is a quick way to tell if a piece of scrimshaw is real or not, if you ever come across a questionable piece.
Some clay pipe heads were made using molds I guess so it could be clay.
To check if it's plastic there is always the "tooth" trick.
Teeth are very sensitive to texture and material, so taping an object against a front tooth let's you know if it's plastic or clay. Can be used to distinguish between glass-bone-ivory and plastic aswell.