No, it's definitely an electret. 1mm X 6mm. The rubber housing it's in is bigger than it is. I did a continuity test, one of the leads is connected to the case although there's no sign of it on the external pad. I never tested for dynamic response, basically just a tap test to see if I got anything so I might not be getting any gain when it's reverse biased, but definitely getting something. The bias voltage of the sound card is only 2 volts and I've seen circuits on the net that suggest biasing much higher, like 9+ volts to get decent response from them, so even properly biased it might not be getting much gain.
I've heard of basic JFets working in both directions before, because they don't have the body diode like a MosFet does right?