Replica plane diffraction grating, area 49 x 36 mm, mounted on glass plate with label reading 'Thorp's Transparent Replica of Rowland's / Metal Diffraction Grating / 14505 lines to the inch', and with 'The original is the property of Dr Common / Thomas Thorp / Whitefield [ . . . . ] / Oct 1906' [one word is indecipherable: reading of the year is also uncertain] written in white ink on the black edging tape. Replica plane diffraction grating 1906, October
Direct vision grating pocket microscope with adjustable slit made by T. Thorp, Manchester, with case, 1890-1900. Direct vision grating pocket microscope with adjustable slit 1890-1900