ECO A48
London System, with Bd3
The position after 1.d4 Nf6 2.Nf3 g6 3.Bf4 Bg7 4.e3 d6 5.Bd3.
1. d4 Nf6 2. Nf3 g6 3. Bf4 Bg7 4. e3 d6 5. Bd3
London System, with Bd3 is filed under ECO A48, a variation of London System. It is the position after 1.d4 Nf6 2.Nf3 g6 3.Bf4 Bg7 4.e3 d6 5.Bd3 — 9 half-moves in, with Black to move. Named theory ends here; beyond this the position is yours to work out.