Manufacturer's part #01 LAO 022. Original price: $40.00. Made of crown and flint glasses NOT cemented. Surface accuracy is 1/4 wave at 546.1nm, design wavelength of 488, 546.1, 643.8nm. Clear aperture of 7.2mm, center thickness is 4.5mm, edge thickness is 3.9mm, surface quality is 60-40 scratch and dig, centration of 3 arc minutes. Unused.