Apparatus for testing keenness of eyesight. After Galton, by Cambr. Scient. Instr. Co.   See also <link ref="tec3099">another figure</link> of this instrument on another photograph from Harvard.  
Galton's Apparatus for testing keenness of eyesight is also described by the Cambridge Scientific Instrument Company, in <link ref="lit38593" page="p0006"  mk="0.3251/0.8433">"A descriptive list of anthropometric apparatus"</link> (1887).
For an updated version, see  <link href="http://www.sil.si.edu/digitalcollections/trade-literature/scientific-instruments/files/51682/imagepages/image116.htm">Cambridge, 1899</link>. Apparatus for testing keenness of eyesight. After Galton, by Cambr. Scient. Instr. Co. 
        
        
          
          
        
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