5 lug pot?

I have this tube amp of uncertain origin that has a nice complement of tubes & looks like it could make a nice little guitar amp. I'm starting to trace a schematic for it, but the volume pot has me confused. It's got the usual 3 lugs on one side, plus another 2 lugs on the other. I don't really want to take the pot out of circuit to ohm it out at this point, so I was wondering if anyone could explain the configuration of this thing.

Thanks
Tom

Power switch or taps.

Taps if no extarnal add on switch visdible on the back of the pot.

Does it have a detent click thingy?

No switch. Here's a pic:
http://home.att.net/~giuseppe_poteet/5lug.jpg

This shows the 2 lugs on the opposite side from the usual 3. I've seen this style pot before but never had any call to know what it did.

[quote author="hodad"]
This shows the 2 lugs on the opposite side from the usual 3. I've seen this style pot before but never had any call to know what it did.[/quote]
What's the function of this pot ? Volume I guess. A tap could then be used for a loudness-circuit, switching in or out of a few caps/resistors to give loudness-functionality.
I recall a circuit with one tap (Marantz-amp), but two will do something alike I guess.

If it's not a volume-control then please ignore.

Bye,

Peter

Back in 30'th there were experiments conductetd suggesting that human perceptions of lower end of frequencies depend on volume level, and some "equal loudness" curves were obtained.

However, while the topic of subjectivity is questionable since it could be resulted from used equipment, the idea of better usage of amplifier's power on low levels for better bass response is good, so lot of amplifiers that era implemented it. Volume pots with additional taps were made exactly for such purpose, to increase bass levels on low volumes.

It's up to you to decide, do you need more bass level on low volumes, or not. I don't think it is needed for a guitar amp, you need 82 Hz bottom end only.