ECO D54: Queen's Gambit Declined

ECO D54 is part of volume D — Closed & Semi-Closed Games. The Lichess chess-openings dataset files one named line under it. It is Queen's Gambit Declined: Neo-Orthodox Variation: 1. d4 Nf6 2. c4 e6 3. Nc3 d5 4. Bg5 Be7 5. e3 O-O 6. Rc1.

That position has come up in 32,803 Lichess games between players rated 1600 to 2500: White won 52.1%, 6.2% were drawn and Black won 41.7%.