a Stokes lens, or variable power cross cylinder lens, for measuring astigmatism. Austrian, late 19th century, by F Fritsch, Wien, in nickel silver and lacquered brass, in fitted chamois lined leather covered case, instrument 14.3cm; with a French scotometer by Luer, Paris, engraved ' Scotometre du Dr A Antonelli' in black oxidesed brass with ebony handle, in fitted velvet and silk lined case covered in brown Morocco, assembled instrument 21cm[