I may be 100% wrong, but I'd bet lymen or RCBS dose not make weights or have a company make weights just for them. The most likely purchase them from a company that makes weights, gage-pins, joe-blocks, etc.. All made toset standards. These standardsmay have diferent +/- ranges but still fall into a known standard. Its not uncommon to findone non-comforming bullet in box. I foundone in a box of speer bullets slightly different ogive and point profile. Measured .358 dia. and seemed to weight 180grs, but I just tossed it.