Manufacturer's part #01 LAO 519. Original price: $74.00. Made of crown and flint glasses (not cemented, but we sell balsam), design wavelengths are 486.1nm, 589nm, and 656.3nm. 25mm diameter with a focal length of 90mm. Edge thickness is 4.4mm, center thickness is 6.5mm. Edges have a .25 - .50mm bevel. Unused.