Banister, H. (1927). Block capital letters as tests of visual acuity. British Journal of Ophthalmology, 11, 49-61.
Produced three matrices: The first two were apparently two
different sets of participants in the same experiment (Exp. 1), which
used briefly-presented letters presented at a distance. The
third matrix (Exp. 3) used letters presented at a distance
for long duration.
The characters were Dr. John Green's uppercase lettering set
(an alternative to Snellen's characters) that were presented to the American
Ophthalmological Society meeting in 1866 and 1868.
Reproduction of chart below (Currently unable to find full
alphabet of letters).