The "L" frames were introduced in mid 1980,June?? the 581 and the 586......or their 'stainless ' counterparts 680 & 686............we had some in the two piece boxes and then the one piece soon after.....got them from two different 'LE' distributors........'when they started to 'computerize' the labels (bar codes, etc) they needed more room ( bigger labels)? went to larger boxes, ,one piece, more generic, could fit MORE ,different stuff, in the same type box, save time, save money......