What exactly makes you believe that it was struck on a silver planchet? I believe it has just suffered a lot of post-mint damage.
I doubt it is a silver planchet. The early Indian Heads and Flying Eagles were copper nickel. 88% Cu and 12% Ni. Accounting for a whiter colored coin.
Not silver. Your coin is suffering from ED or Environmental Damage. In it's condition you'll never know if it has the L or not. It's too corroded. It's worth about face value to a quarter.
...although it would likely bring at least a buck or two on eBay. As for the L, only a few copper-nickel 1864-L cents are known, right? In general, only copper 1864 cents can have the L.
http://uspatterns.com/incenondimpl.html In mint state (uncirculated/undamaged) these are five-figure coins. As badly damaged as your coin is, an actual silver-planchet cent would still be worth quite a bit -- but as others have said, yours isn't one.
Lol on eBay as the sky is the limit. This is the 1864 Copper-Nickel with Oak Leaf and Shield reverse. Too bad is severely damaged as it's the rare type without the L. Yes a few with an L exist but we'll never know if this was one of them.
Not much due to the condition. It may be corroded enough to make authentication impossible to tell it wasn't created by someone now.