Buried Treasure!

Today was rather exciting, as we found buried treasure in my garden! My father-in-law was helping me dig over the allotment and he found an old coin. The date on the coin is 1735, which makes it really old in my colonial eyes. I cleaned it up a bit to have a better look at it and as much as we can tell, it's not a British coin. Here's a couple of pictures of both sides.
You can see the date at the bottom of the coin, 1735. Above it looks like three letters, Η Γ Α. Above that looks like it's less clear, but looks like a fancy A, with the middle cross bar extending past the angled sides, followed by possibly an F. 

This side is far more difficult to decipher. We think the bit to the left of the corrosion at the top might be a bird head and neck, with a wing on the right side of it. But it might not be, it might be a scroll, it might be anything. This picture is actually pretty good, you aren't missing anything in the photo that we can see in person. 

So if anyone out there has ideas of what this coin might be, or where to research it more, please leave a comment! 

EDIT: Through the power of the internet and my supergoogling friend, Babs, we have found that the coin is a Russian Denga. Not worth a fortune, but an interesting find. What is even more interesting is to ponder how it ended up in an allotment plot in Cookham???