It's a rigid conical strainer used in food preparation. Not to be confused with a chinois which is a French conical strainer with a very fine flexible mesh. If making a large batch of stock let's say, I'd use the china cap to strain out the large solids then run the liquid through the chinois to get the sediment. A good chinois is very handy when making sauces, pureeing soups etc...
You don't often see a 10" china cap outside of a commercial kitchen. I bought a set of several some years ago and never used the large one. It fits well over a 5 gal bucket.
http://www.atlantafixture.com/ItemDe...FWQ0Qgod5RkvUg
-spence