Although this microscope
superficially resembles some models made by the Bausch
& Lomb Optical Co. at the end of the
19th century, a detailed analysis of the
construction suggests that this firm did not make the
microscope (however, the optics are by B&L).
Since except for the
present example, Jno Ehrmann is an unknown maker, it
is most likely that the 1905 engraved on the
microscope is a date and not a serial number.