Microscope Museum

Collection of antique microscopes and other scientific instruments

Microscope 491 (unassigned maker; folding linen tester; late 19^th century to the early 20^th century)

Microscope 491 is a linen tester, or linen prover, and should be dated from the late 19^th century to the early 20^th century. This instrument would be used for counting threads in fabrics (the number of threads per unit of length provides evidence of a higher quality of cloth). The earliest forms have a simple standard opening on the base, but later versions have this opening marked with calibrations of some kind. Microscope 491 is a folding linen tester, and the instrument fold flat for storing and transport and forms a 'C' shape when in use. These linen testers have been made and sold by many companies since at least the early 19th century and were rarely signed by their makers or retailers (Figure 1).

Figure 1. Folding linen testers engraved in the catalogues of several companies: (A) Palmer (1840); (B) Negretti and Zambra (1859); (C, D) William McAllister (1867); (E, F) Negretti and Zambra (1870s e 1885); (G) James Queen (1870 and 1872); (H) Ernest Goldbacher (1879); (I) B. Kahn & Son (c. 1890); (J) Bausch and Lomb (1892); (K) Arthur Thomas (1914); (L) Bausch and Lomb (1914); (M) A. Clarkson & Co (1920s); (N) Emille Deyrolle (1931); and (O, P, Q) Gallenkamp (c. 1939)