Manufacturer's part #01 LAO 018. Original price: $62.00. Made of crown and flint glasses cemented together. Surface accuracy is 1/4 wave at 546.1nm, design wavelength of 488, 546.1, 643.8nm. Center wavelength (with coating) is 550nm. Clear aperture of 7.2mm, center thickness is 5.1mm, edge thickness is 4.4mm, surface quality is 60-40 scratch and dig, centration of 3 arc minutes. Has a great bluish/purple Broadband Anti-Reflective coating. Unused.