DESCRIPTION:

This is an aplanatic Zeiss Thread Counter. It features a 6X Zeiss aplanatic magnifier, adjustable focusing, an attachable screw-driven pointer, and two standardized inserts. One insert is 1/4 inch square, the other a one inch long rectangle. As shown to the left, the base has two concentric rings, the bottom one being fixed. The inserts fit a ledge in the bottom ring and the top ring rotates into place to hold one of the inserts in the groove.

The aplanatic magnifier(left) is signed in the Zeiss lens-shaped logo CARL ZEISS, JENA and with the magnification 6x. The base(right) is also signed on the top ring CARL ZEISS JENA.

The two inserts are labeled on their tab-handles 1/4"engl.,=6.55,mm and 1"engl.,=25.4, mm respectively. They fit into the fixed bottom ring of the base and with the tab handles protruding when the top ring is swung over them to hold them in place. The tab rides in a groove in the bottom plate, allowing the openings to be parallel to the pointer, or up to 45 degrees from that configuration providing a diamond-shaped opening. This instrument was originally supplied with a set of up to 6 or 7 inserts including the English 1/4 inch and 1 inch seen here, but also a 1/4 French inch =6.77 mm, a 2 cm, and a 1 French inch.

The focusing is a sliding slotted design with a screw(green arrow) riding in the slot, keeping the sliding rod vertical and a knurled knob(red arrow) to lock the focusing height as desired. A later version had knob-focusing via an offset pin but I was unable to locate a Zeiss catalog which showed this version.

The case has box joints and a slide off top. Inside, the compartments keep the instrument organized. The magnifier, with its attached mounting, is stored in one of three angled blocks; the other two blocks could accept the two other optional (8X and 10X) magnifiers, supplied in their own mounts, and offered in the 1934 and 1939 catalogs.

HISTORY OF ZEISS APLANATIC THREAD COUNTERS:
Although Zeiss offered aplanatic magnifiers before, the basic form of this device for thread counting was first offered around 1924. That version had a handle attached, came with insert(s) but did not have the moving pointer shown in the one featured at the top of this page.

In 1927, the catalog showed the same one as in 1924, but the handle was no longer pictured, yet in the French 1930 edition of the Zeiss catalog, the one with the handle was again pictured.

In the 1934 and 1939 catalogs the model featured above on this page with the moving pointer was listed and illustrated. It was supplied with two different calibrated inserts for the base, and with a different calibrated insert, but not the moving pointer, it was offered as a measuring magnifier. In addition, an electrically lighted thread counter, which came with a greater number of standard inserts, was also listed.

For the general history of linen testers and thread counters please see the page on their history.