Typical and Non-Typical Variation of the Frogman, Model 6334
The Red and Black Handle are common models.
The Flat Black Handle (shown upper right ) is Military / Nato Model.

These Models shown, we think,  were made from about 1966 through 1979
The Nato Model, we think ,was made for two years about 1983-84
Not shown is a variation with Yellow Sheath..