But I can tell you one easy & simple, being accurate most of the time w/ exceptions I sure, method to quickly discern whether 1st or 2nd series & that is to note Brown/Plum on the colour of the tubes on the 1st set(possibly including a few up to the Crown/Sidearms transition to HAL/Sidearms) & Black on the 2nd, whether pattern welded or fluid steel.

Cheers,

Raimey
rse