Yo, Nick --
If you in fact have a genuine Martha Washington pattern coin, you've really *got something*. Values of your coin could easily rise into the 1000s of US dollars. You see, private individuals were not supposed to have access to these coins when they were struck in recent times. The 1759 date is bogus. Coins like these were made in the later part of the 20th century.
The Mint somegimes tests new coins with what they call 'nonsense dies.' These dies, the hard pieces of metal used to strike coins from softer metal, are used in testing the minting process. Coins struck during these tests are supposed to be controlled by the Mint and not releaed into circulation.
At MintErrorNews.com there is a price guide for these pieces. Here is a summary. Coins must be absolutely, fully uncirculated to meet these price levels. Our estimates are lower than Mint Error News based on experience we have had with these coins.
Cents and nickels: $200 fully uncirculated
Quarters and halves: $2000
These are catalog values for fully uncirculated coins. Coins with wear will be worth much less. Coins with damage will be worth almost zero. Use our Terminology page to convert catalog values to actual buy and sell values.
There may be counterfeits of these valuable pieces. I am not sure if counterfeits exist, but it is a possibility. Can you send a picture of your coin to CoinQuest? We will be able to tell you much more if we see a picture. We cannot really ascertain value unless we see a picture. If you have a genuine coin, there are several steps you should take immediately to protect its value.
DO NOT CLEAN YOUR COIN. CLEANING RUINS VALUE.
To send a picture, put your coin on a scanner or take a picture in macro mode, flash off, with a digital camera. Then use the Contact Us link to start an e-mail exchange with CoinQuest.
CoinQuest thanks Mike Byers Numismatics for use of their coin image. Mike literally wrote the book about coins such as yours.