Original Iletin--1923. This was made of beef and was Regular/neutral insulin. The 2 vial cartons illustrate the strengths insulin came in at the time; the carton on the left is U20 strength while the one on the right is U40.
Eli Lilly and Company[1] is an American pharmaceuticals giant from Indianapolis. Eli Lilly has been producing insulins commercially since 1923.
Studies done on all Lilly vialed insulins--Humulin, Iletin, and Humalog, show that the stoppers have sufficient resealing properties to maintain a good seal after 100 punctures. What this means to you is that the insulin will stay potent longer[2].
More on the company and its products here.