It's always risky identifying a knife without seeing it, but I'm sure you have what Joe Houser calls a 5th Version, Variation 3. George Stinzel has a different classification system and calls it 3rd Version, Type 6. Houser gives a date of 1972-1974. Stinzel gives a date of 1974-1975. I think 1974, give or take a little, is probably about right.
Bert