I was somewhat fortunate to win my game of chess tonight. In the spirit of the season my opponent missed a simple pin and gave me a piece quite early on. But what I found interesting about the game was that we had followed some old opening theory for quite a while. This was mainly due to the fact that I tried to play the Dutch against 1.Nf3 and my opponent then wheeled out 2.e4 (the Lisitsin Gambit) to put me on the spot. Despite having never played the Latvian Gambit in a serious game before I decided to meet gambit with gambit and played 2. ... e5. Certainly I was in uncharted waters but my opponent said that the Latvian is an occupational hazard if you play the Lisitsin (as he does).
Despite my unfamiliarity with it all we managed to follow theory for a reasonable number of moves ( 3.Nxe5 Qf6 4.d4 d6 5.Nc4 fxe4 6.Nc3 Bf5 7.Ne3 c6 8.d5 Nd7 9.Be2 ) before I finally stumbled upon a new move. 9. ...Ne7N was what I found, but I suspect it doesn't improve upon previous theory. However it does seem to be the first new move in this line since 1876. Doing a bit of checking, this may be the oldest line that I have played a new move in, although I would probably need to do some more exhaustive research to be sure.
For interest sake the original game went 9...Be7 10.0-0 Nh6 11.f3 exf3 12.Bxf3 Qe5 13.dxc6 bxc6 14.Bxc6 Rd8 15.Qh5+ Bg6 16.Ned5 Nf5 17.Nc7+ Kf8 18.Qf3 Nf6 19.Bd5 Nd4 20.Qf2 Rc8 21.Bf4 Qh5 22.Ne6+ Nxe6 23.Bxe6 Rc5 24.Rad1 Salvioli-D'Aumiller,A/Venetie 1876/1-0 so at least I scored a better result than D'Aumiller.