340 K Member ??

Yeah, what's up with that? Even the rare ones got the 'washer' - my '72 Swinger 340 Special has one and the guys up here with the '71 Swinger 340 Specials have got them as well. At first I thought it was only these 'special' order Swingers but I checked my '70 340 Swinger and it has it too. Has to be some kind of assembly line ID thing...