dsmegstHi @dsmegst, there are two easy ways to tell them apart.
1) Plug the mic in, hit record, and rotate it slowly in your hand while talking in a normal voice. The Uni-directional should clearly fade in and out as you rotate. The omni will not.
2) If you remove the foam pop filter you should be able to see one has holes pointing in only one direction. However, I do not reccomend this as you may damage the filter (which, while cheap, means we'd have to ship you a new one!)
brolly@brolly and @dsmegst that is correct, the mic symbol indicates what direction the mic is pointing (though I believe the symbol is on the Omni as well, which is a bit strange I admit).
AntlionJoeOk, using record and rotating the mic, I figured them out and now clearly marked the Uni as such. Just FYI, I did check under the pads and they both had holes front and back. Visually no difference. But one clearly was Uni and the other Omni by sound. Thank you.