Anyone that is familiar with or owns Lumley Megavox 150s? I have questions.

I've been listening to the Raymond Lumley Megavox 150 tube monoblocks for a couple of months now, and I like what I'm hearing, but it's very difficult to find information about them online, so I'd like to hear from anyone with knowledge of them. First up, mine have a pot on the rear panel, midway between the RCA input and the IEC socket, which I recall the seller referred to as a gain control. It seems to not have any effect when I adjust it while listening, maybe it was disconnected...? Second, If you've run these, what is your optimal setting advice re bias? For now I've set the bias just shy of 50mA on the meter on the front panel. From 50 to 65 on the meter there's a red band, and I don't know if that means "set bias within this range" or "up to here, but no further". I'm open to any comment, but hope to connect with someone who has these in their system.