Posted By Diane Warne Nick, I think the 1b39 may be the frame/lens marks(under EN166) for the particular type of eye protection you are looking at. If 1 is a lens mark that is probably refractive tolerance which is measured 1 to 3, 1 being the best (least distorting.) B is impact resistance "Medium" or Grade 1, i.e. up to 120m/s velocity, equal to the old BS2092:1. 3 and 9 are about what it protects against, 3 being liquids (chemical) and 9 being molten metals and hot solids. I got all this from a table I copied from somewhere about BSEN marnings - I think it's right, but it might be best to check with the manufacturer. Best wishes Diane