Is there an easy way to tell a stainless Perlick faucet from a chrome plated one if I have physical access to them and they aren't connected to a shank or anything?
Not connected to a shank?
Look into the bore, where the shank goes in.
If it's chrome plated, the "plate" will look a little dull within, ( no, a lot dull), because when plated, there is no anode with a line of sight into the bore.
If a well used chrome plated one, look in the delivery end, and search for signs of plating flaking off.
Stainless:, you should be able to see some obvious machining marks within, and the luster of the metal will be similar to the outside, sans the high buff polish job.
Edit: might sound a little funny, but chrome plating will have a "slightly yellowish" hue to it, due to the "nickel strike" plating done over the base metal, ( or copper plating, if used),and the hue can be detected through the chrome plating.
Very obvious, if the two metals of construction are side by side.