At a glance, stainless steel is normally slightly duller than chrome. Chrome plating has a greater possibility of pitting and rusting. Although, martensetic stainless steel can rust.
Fully annealed austenitic stainless steel is not highly magnetic, where as most metals that are plated with chrome are. Simple magnet test may make the determination easy, but some stainless steel has enough nickel to make it slightly magnetic.
If the results of the magnet test are inconclusive, chrome is passive to most chemical corrosives or agents, Cu So4 being a good one to tell steel from chrome, as steel reacts and deposits copper on the surface. Test in a small area not readily visible for a better answer.
This advice was swiped from the internets via the google, as I am not this knowledgeable on this subject on my own
