Set of color-disks, 60 ctm. in diameter. By Krille, Leipzig
Source
Anonymous. 1892. Harvard Psychological Laboratory in Dane Hall: Instruments for Experiments on Sight. Photograph. (Harvard University Archives - HUPSF Psychological Laboratories (7))
See more color disks on another photograph from the same set (here and here). These discs have probably been used for the Large color-mixer for four disks shown on the same photograph.