Courtesy of Dan Cooper from the Facebook Trilobites group, a rare Isotelus eye with lenses preserved.
The claim for this specimen is ~1000 eye lenses, but with all due respect, much closer to ~5000 lenses.
Do the math!
table from:
Rose, J.N. (1968)
The eyes of Isotelus and Nileus.
Proceedings of the Iowa Academy of Science, 74:178-185