Thanks Chris, good photos. That is the AS-1729 antenna with MX-6707 base. It is intended for use on 30 to 76 MHz and has the switch to set the internal components for the range needed. That switch can be set manually, as you noted, or electrically by way of the multi-pin connector (only turn it clockwise.) The switching signal can come from the typical VRC-12 radio set, like the RT-524 or RT-246.
There is a great website here:
http://radionerds.com/index.php/AS-1729~VRC with most any info you need on the antenna. This antenna works fine for 6 meter ham and sort of works on 10m Ham band and 11 meters(CB) but don't expect best performance. For receiving, it will work just fine.
The coaxial connector is a standard BNC type, same as used on the radios, so a BNC to BNC coaxial cable is used.