Audiolab 8000Q preamp?

Audiolab was a highly respected british manufacturer, I would say more highly regarded than Quad in England. They were bought out by TagHeuer, so you don't see the name anymore. Audiolab equipment is renowned for being neutral and accurate. It's not to everyone's tastes, but it might explain why it works well in a system with valves elsewhere in the signal path.
Used audiolab equipment is tremendous value in the US due to its obscurity.

Agree with Hdm. Audiolab produced very good, high quality products. You've got a great amp there. Audiolab was a no-frills company so the casing looks cheaper than some of its competitor, but taking the lid off reveals a well designed and high quality PCB. It should last 20 years.
Leaving it on is probably best, unless there's a lightning storm nearby in which case unplug it completely. Constantly switching it on and off leads causes it to heat and cool, which causes the components to expand and contract. This can cause component failure, most usually in the electrolytic capacitors.