Looks like one of those fat reducing jobs, you fill the chrome tray bit with water for somereason. Sure someone who acctuly knows will be along shortly.
It's a griddle plate, for use on a gas hob. The stainless tray surrounds the burner, and the black plate goes on top. I'd imagine any fat which runs off will be collected in the stainless tray.
Northerner guz to t’jewellers, sez, "Can tha mek a gold statue o' mi dog?". "Aye, reckon a can," sez jeweller, "does tha want it eighteen carat?". "Neigh," sez bloke, "I want it chewin' a bone."