Stamped 1840 Farthing

Sorry I don't, but often you come across coins which have one side smoothed down and then carve their initials into it. These "love tokens" were then given to their partners for keepsakes. Sometimes people just liked to personalise a coin as a lucky charm or pocket piece.

yes it does look like its done by machine, they've really damaged the coin to do it. I wonder if he did lots of coins or just this one.

It would have most likely been done for advertising purposes, and was quite common until laws were passed to prevent this very thing.

I assume you found it in Australia, blueczar? Such a counterstamp could have been applied in Australia, or it could have been done back in the Old Country, or even in another British colony.

Some studies of advertising countermarks have been made, and there are some folks who collect them. The very first issue of the Queensland Numismatic Society Magazine in July 1986 contains an article on countermarks found on Australian trade tokens; unfortunately, "W. Nash" isn't on this list. Searching the web, this guy has written a book on world advertising countermarks, and lists all the ones he knows about on his website; "W. Nash" isn't on his list, either.