I'm seeking help in identifying this potentiometer in order to find a suitable replacement and/or to understand its pinout. It is a thumbwheel volume control from a circa 2005 external computer speakers control. 
The measure top of frame is in millimeters. The upper tabs were soldered, but I'm pretty sure they were only for mechanical support against the PCB.
The thumbwheel diameter is ~20mm, the manufacturer mark seems to be Delta, and through the oval window is the designation "C103." Difficult to see in the lighting, but it's C103.
I would take ohm readings between the pins, but this is the part that failed, so I do not trust any readings I get. I have looked on Digikey and of course I see many potentiometers, but most with three contacts and some with six — but I cannot find one with five contacts. Can someone suggest what might be a suitable replacement for this, or what exactly this is so that I can find a datasheet that explains the pinout?
EDIT: Questions in comments addressed:
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This is not an on-off switch. The unit is switched on and off using a toggle pushbutton located elsewhere on the PCB. That switch works properly.
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I do not think this is an encoder; the thumbwheel rotates through about 300°, not quite a full revolution. When it worked properly, volume increased steadily from one extreme of rotation, from silent to full volume. There were no audible "steps." It failed slowly. At first, there was a loud popping and static when adjusting volume. Then fewer settings would work. Then no adjustment was possible and only a particular setting worked. Finally, I was moving stuff around on the desk and it moved again, and I was unable to ever find the "working spot" again.
I'd love to fix this because I really like the sound from this old external speaker — the bass/subwoofer is particularly good for its size and price.
Best Answer
Digikey has this part, which looks similar:
Do the sizes and pin locations match?
103 is almost certainly a 10k pot. You can try checking the rough resistance values, or if you can crack off the knob, you can likely infer the topology from the resistive layer geometry.
If this isn't an exact match, hopefully it provides a starting point for further search, and an idea what the five pins might be doing on a pot.