I would use it for a PS for a tube amp.
Its is also probably OK for 380VAC and you most likely won't have a problem. The thing is that you never know when there will be a problem on the line, like a spike, that could kill the meter or injure you. Personally I would avoid using it for that use, but you will almost always have no problem. It is the infrequent occurrence that hurts or kills someone that causes meters to need the safety ratings that we have now.