If the tubes are not marked on the bases you have little choice. Do you have a multi meter? After the amps have warmed up for about 15 minutes. I would test the bias of the power tubes. See how close the secondary tubes are to 65ma and if necessary move the tubes around.
I assume that you bought the amp used so you do not know how many hours are really on the power tubes. If it were me I would buy a new set of power tubes and keep the old ones as spares. You want to get either two matched pairs or a matched quad. I would also see if you could find a place to have the old tubes tested.