realize the barrels will likely be metric - 70CM will come out to about 27 1/2 inches - some are light bird guns but some tend to be heavier. it doesn't hurt to ask the weight

Sauer is a good standard to measure to but as Ed says - hard to find a prewar gun that - assuming proper condition - you wouldn't be happy with. The proof date in on the water table for a German gun made between the wars - i forget when it became standard