They used Stat Exp. instead of EVs in RBY and GSC. Basically, you gain some after you defeat a Pokemon. You can have a max of 65536 Stat Exp. It affects all stats - not just one or two like EVs. Vitamins add 2560 (?) Stat Exp. each.
If we take two of the same Pokemon with the same DVs and RC one and hand-train the other, the hand-trained one will always be stronger across the board.
It's not that simple with damage. It's really:
Damage: (((((((Level × 2 ÷ 5) + 2) × BasePower × [Sp]Atk ÷ 50) ÷ [Sp]Def) × Mod1) + 2) ×
CH × Mod2 × R ÷ 100) × STAB × Type1 × Type2 × Mod3
There's a bunch of Modifiers and Type issues, and the level is important. A lv2 Rattata can't deal 35 damage to a lv2 Pidgey by Tackling.
For the full article see Smogon: