Mallory, based on your description...
the chips sounds like a chip from a home poker set, which means that it probably has a value of about $5. I say this because $50 is an unusual denomination for a casino chip and a lone letter is more indicitive of a home poker set of chips, or a chip from an "illegal joint" long out of operation. Please note that some illegal joint chips may have a larger collector value, but it is uncertain until a better description (or picture) is obtained.
Included here is a scan of two different chips I have that remind me of your description. Both have the distinctive top hat and cane (what we call a hat and cane mold) a very common mold used in casinos, illegal joints and home poker sets for quite some time.
Does the "$50.00" look like yours? How about the letter "Z"? Note also the manner in which the lettering is stamped onto the chips. Is it the same for yours?
Jim Follis