I think there are both porcelain crowns (which may also have some resin or acrylic parts), and then there are metal crowns with porcelain bonded to them on the outside. Sounds like you got the latter.
OK, I’m no dental expert, but I googled for “metal-free crowns” and it appears that they use some kind of tooth-colored zirconium oxide for the inner part.
Feel free to correct me if you know more about dentistry than I do (which wouldn’t be very hard!)
Well, I’ll have to do research. I did look in my Schedule of Services, shows:
Crown - porcelain fused to high noble metal $629
Crown - porcelain fused to predominately base metal $590
Crown - full cast high noble metal $608
Crown - full cast predominately base metal $532
And then the temporary stainless steel crowns