This is the flint element for the Jaegers 6 inch by 90 inch telescope objective. Index is 1.621. Abbe V#: 36.2. R1: -32.346, R2: +128.00. There is coating breakup that doesn’t appear to effect its use. These were marked stria so it probably won’t be good for use as part of an objective but works well for other uses. Very limited supply