Vintage Carl ZEISS JENA Abbe's Test Plate, with case

Description

Vintage Carl ZEISS JENA Abbe's Test Plate, with case.
The Test Plate consist of a series of six coverglasses, ranging in thicknesses from 0.09 to 00.24mm - the positions are 0.09, 0.11, 0.15, 0.18, 0.21, and 0.24.  Groups of parallel lines are cut through the thin silvered film on the underside of each coverglass iteration.  The Abbe Test Plate is intended for the examination of the objective with respect to both spherical and chromatic aberrations.  It can also be used to determine the optimum coverglass thickness for which a particular objective is corrected.  Although a vintage, and collectable, it is still useful for its intended purpose.
Note:  As can be expected from the age of this preparation, there is peripheral compromise in the coverglass mountant at most of the positions.  However, its usefulness is not diminished, even at low power objective, when using the central 60% or so.  Still a very effective Test Plate.
The case is nothing to write home about - cotton pads at each end with loose top cover (repairable).  The Sale label may not have been related to this Test Plate, but they came together.
The shipping charge is for Priority Mail within the U.S.  No International Shipping is available.