A capital alphabet drawn by Walter Haettenschweiler with a Rapidograph technical pen and reproduced in Lettera 3 (1968). The name is derived from the OP Art movement. [Swiss Type Design] In the sample, the missing ‘P’ was made from ‘R’.
A very similar film typeface is shown in Lettergraphics’ 1968 specimen as Fat Albert, together with a solid version named Albert. Compared to OP-Letter, Fat Albert has harmonized letter heights, ‘H’ is more even, shadows in ‘C’, ‘F’, ‘R’ are different.