Fisher vs spassky 1972 game 6- ECO:D59 not A13...Why????

Hi,

I am puzzled why that game is listed as ECO D59 and not A13.

http://www.chessgames.com/perl/chessgame?gid=1044366

ECO A13: 1. c4 e6 2. Nf3 d5
ECO D59: 1. d4 d5 2. c4 e6 3. Nc3 Nf6 4. Bg5 Be7 5. e3 O-O 6. Nf3 h6 7. Bh4 b6 8. cxd5 Nxd5

Does anyone know why?

It transposes to QGD on white's 3rd move.

[edit]According to SCID, starts A13, then D30(3), D37(4),D53(5),D55(6),D58(...7),D59(8), QGD, Tartakower

Okay, thanks.

I am new to this ECO stuff. If I add ECO to my games, how do I know when to transpose it? What are the rules/pointer to do this?

Well, I just look what Scid says, I'm not too concerned what ECO it is.

It kinda makes sense that the opening name(or ECO) is deriveed from the latest position, not the earliest.

If your into hs kinda stuff, download Scid, and a decent database, and let Scid eco-classify your DB

Ok, Thanks for the information :-)