Shadowguy was right, my snake is a female. I had her probed at a local reptile dealer. A very experienced herper, he charged only $10 to probe.

(The local "exotic" veterinary charges $50 for a general snake examination. They do not allow a la carte pricing to only sex snakes - which is why they just lost $10.)

0.1 Pituophis catenifer catenifer
0.1 Pantherophis guttatus (Carolina phase)
1.0 Pituophis catenifer catenifer (wild in back yard nature zone)