Identifying & Valuing Antique Silver Snifters by Wm Rogers & Sons

Question
I have a pair of silver (brandy?) snifters.  There is a stam on the bottom that says "Wm Rogers & Sons."  Is there a way to tell if they are silver or silver plate?  They have been in my family for some time, but I don't know where to begin to figure out how old they are or an estimated value.  Can you point me in the right direction.  Thank you.

Answer
Greetings,

I am not personally familiar with this company, but they seem to be quite illustrious.
Have a look at this site as a start....

http://www.centennialantiques.com/WmRogers.html

Think you'll need to library, antique shop and google this one.
Good Luck, P