It's one of the new fangled SMA-type connectors, strengthened with an added threaded cap. I'm not sure if the antenna-to-radio interface is an industry-standard design or not.
Geesh, the last time I bought a Ham radio walkie-talkie was in 1984 (an Icom IC-02AT bought in Hong Kong).
The antenna looks fine and does work (obviously), but others have reported that aftermarket antennas provide better RF performance. I can't comment since I have nothing to compare the included antenna against.