Well, voltage ratios are easy, as I said. Max voltage cannot be measured, as it depends on the insulation. You can, however, make insulation assumptions for the primary winding if you know where the xformer came from (eg. a mains transformer pulled from most european user equipment will handle 240V).. You can calculate max power if you can get a good estimate of the cross-sectional area of the winding's wire, usually the same wire connecting to the Xformer terminal. Knowing the resistance of the winding (ohmmeter) and the cross-sectional area of the conductor, you can get a good idea of it's length..