Dual Terror Trim pot??

[Jondog]

Just scored a Dual Terror, and I'm in the process of building a shell for it. So I took the bottom plate off for some measurements and noticed a trim pot inside. I know these don't need biasing, but it reads "Hum Balance" beside the trim pot. Is this something that can be used to improve the sound of the amp if it is humming more then usual? Never seen one of these before in an amp. Just curious, not going to mess with it as the amp is running just fine.