The condenser lens is engraved “2/7in. 1.0 N.A. Less front lens 4/10 in. 0.35 N.A.” Iris scale engraved 1.0 to .35. The condenser lens mount is RMS objective standard, so different objectives can be utilised as condensers. The condenser also shown with an early 1″ Watson objective N.A. .28 to illustrate this. This iris would have to be stopped right down with this lens.
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Ganymede Antiques, the scientific and medical instrument specialists established in 1992 and based in London, U.K. ceased trading as a business in March 2022. However Keith Petts has for disposal some reference books and scientific instruments personally owned which will be offered on Fleaglass. I no longer purchase scientific or medical instruments. I can be contacted at [email protected]