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Concave spherical lens, a duplicate of part of part 1

Concave spherical lens

Concave spherical lens, 31 pairs, 1 of which is incomplete, forming a series, numbered -0. 12,0.25(0.25)3.50(0.50)7(1)12(2)20

Concave spherical lens

Convex spherical lens, 31 pairs, one of which is incomplete, forming a series, numbered +0. 12, 0.25(0.25)3.50(0.50)7(1)12(2)20

Convex spherical lens