T600 was the Version 1 and T601 was the Version 2. but some V2 are marked T600 because DJI just used up old parts at the begining when switching.
the V1 also has the Camo style carbon fiber main arms, smaller X3 vibration board, and the center frame is upward curved metal lift arms
the V2 is the woven/braided carbon fiber main arms, larger X5 vibration board, motors are marked 3510H, and the center frame has "Y" shaped metal lift arms
the tricky thing is some V2 will have the camo arms and be marked T600, with the older curved lift arms, but have the 3510H motors and larger X5 board.