Since none of those binary options exclude any of the others, 2 * 2 * 2 *2 or 2^4 = 16 is the answer, so the winner is scalpelX.
1) Choil, Round Butt, Heavy Swedge, and Serrations -> [a,a,a,a]
2) Choil, Round Butt, Heavy Swedge, and Plain Edge -> [a,a,a,b]
3) Choil, Round Butt, No Swedge, and Serrations -> [a,a,b,a]
4) Choil, Round Butt, No Swedge, and Plain Edge -> [a,a,b,b]
5) Choil, Skull Crusher Butt, Heavy Swedge, and Serrations -> [a,b,a,a]
6) Choil, Skull Crusher Butt, Heavy Swedge, and Plain Edge -> [a,b,a,b]
7) Choil, Skull Crusher Butt, No Swedge, and Serrations -> [a,b,b,a]
8) Choil, Skull Crusher Butt, No Swedge, and Plain Edge -> [a,b,b,b]
9) No Choil, Round Butt, Heavy Swedge, and Serrations -> [b,a,a,a]
10) No Choil, Round Butt, Heavy Swedge, and Plain Edge -> [b,a,a,b]
11) No Choil, Round Butt, No Swedge, and Serrations -> [b,a,b,a]
12) No Choil, Round Butt, No Swedge, and Plain Edge -> [b,a,b,b]
13) No Choil, Skull Crusher Butt, Heavy Swedge, and Serrations -> [b,b,a,a]
14) No Choil, Skull Crusher Butt, Heavy Swedge, and Plain Edge -> [b,b,a,b]
15) No Choil, Skull Crusher Butt, No Swedge, and Serrations -> [b,b,b,a]
16) No Choil, Skull Crusher Butt, No Swedge, and Plain Edge -> [b,b,b,b]