no idea about this opening

It's a variation of the Scotch, though 4...Nxd4 is usually not played by black since it allows white a nice centralized queen.

scotch game! better is 4...Bc5 with serious complications - actually favoring black!

After 3.d4 it is the Scotch Game. 4...Nxd4 is not usual. 4...Bc5 is popular. Steinitz played 4...Qh4.

 I agree that Black might already be equal after 4...Bc5.  That's why I play the Scotch GAMBIT instead of the Scotch GAME:  1 e4 e5  2 Nf3 Nc6  3 d4 ed  4 Bc4 and then 5 c3.

4...Bc5 is equal?!

4...Bc5 favors black?!!

I am absolutely positive that black has to work harder than that to achieve equal chances, much less have an advantage. There is not a single mainstream opening where black can equalize by move 4. Where did you guys get this idea?

hmmm....... 4.... Bc5 scores 46% so does 4....Nf6 so its not quite equal and certainly does NOT favor black. Whats funny is that 4.... Qh4 scores 48% but noone seems willing to play it ! 

 I suspect that the reason that the Scotch Game is almost never played by GM's is because it is very difficult for White to maintain the initiative for as long as he or she can in many lines of the Ruy Lopez, for example.

On at least one two-million game database, BLACK has a plus score in the Exchange French.  While it would be extravegant to claim that this proves that Black really has an advantage in the Exchange French, it strongly suggests that White doesn't achieve an opening advantage with it on a regular basis.

It obviously doesn't prove anything, but just for giggles and grins I went to the Chesslab.com database and looked at all games from 2007 and 2008 which began 1 e4 e5  2 Nf3 Nc6  3 d4 ed  4 Nd4 Bc5.  I only looked at games in which both players were rated at least 2600.  Here's what I came up with:

White wins...7  (13.7%)

Black wins...12  (23.5%)

Draws........32  (62.7%)

Overall, White scored 45.05% if draws count for 1/2 point.

Like I said, such a small sample (51 games) probably doesn't mean much (if anything), but I thought it might be fun to post the results 

Kasparov has played the Scotch with 3.Nxd4 successfully. When he was playing the Scotch, his aim was to have a new weapon that was not being used at his level. He did not select it by using statistics. Citing statistical results is helpful. However, the choices players make are often specific to the situation. Statistics do not account for that. If the lower rated player is White and plays the French Exchange to avoid other lines, that player is still lower rated and should score under 50%. If the higher rated player plays the same thing because a draw is satisfactory due to the tournament position, a draw is likely and would not be helpful to the winning percentage for the white side. In other situations, they would be likely to choose other variations. So far, nobody has mentioned 3.c3.

I was talking about the position as being equal, or 'offering equal chances,' not scoring equally. I believe that with accurate play, every 4...Bc5 line can probably equalize. However, I doubt this will happen before move 15 or so. Certainly not by move 4!