One of the key factors to help determine value is the condition of the foam type ring on the woofers that attach the cone to the frame. If it's old and cracked value drops badly. Is the other a woofer also or a drone?
Back in the day (lol) they used to put 2 woofers but only one was actually wired. The other just sat there and shared the same resonance chamber and relied on the wired woofer to create the bass. The drone just bounced from the woofers vibrations. It actually enhanced the bass some.