The brand was only as good as their suppliers, notably case suppliers, link in manufacturing link enough Speedies to keep up. Huguenin Freres was the trusted casemaker for pretty much all early Speedmasters with 321 movements, proudly stamped with an "HF" logo inside the caseback. However, link it is believed that Omega had some trouble sourcing cases from HF around 1966 to '68. This trouble resulted in the watch we have here today. link