I tidbit of info on type 1 and type 2 1939 Jefferson's
1939 P Type 1 Rev of 1938 10%
1 in 400 having 5 full steps. 6 steps unknown.
1939 P Type 2 Rev of 1940 90%
scarce but much more available than TY 1 having 5 full steps. 6 full steps very rare.
1939 D Type 1 Rev of 1938 25%
1 in 150 having 5 full steps. 6 steps unverified.
1939 D Type 2 Rev of 1940 75%
1 in 10 5 full steps. 6 full steps very rare.
1939 S Type 1 Rev of 1938 55%
1 in 100 having 5 full steps. 6 steps unverified.
1939 S Type 2 Rev of 1940 45%
1 in 10 5 full steps. 6 full steps very rare.
So generally all business strike 1939
Jefferson nickels are found more often with the 1940 reverse.