Quality stainless steel. The tray is sufficient enough "hollow" to be filled with a thick bed of coarse salt and oysters or crushed ice and seafood. Stainless steel is thick enough to ensure perfect flatness of the plate: the tray is "wrong" not at all. The finish of the plate is excellent.
No rust task to date. No negative to report so far.
In conclusion, the seafood platter is very good or excellent. I recommend.
