A simple test using not much more than a DMM:
First, using either the diode mode or a resistance mode, identify the two PN diodes in the NPN structure and their forward direction.
Then, use a 9 V battery in series with, say, 40 k ohms (anywhere from 30 to 50 would do).
Connect that to the 10 megohm input of the DMM in voltage mode, and you will measure close to 9 V.
Connect that to each of these diodes:
If you measure < 1 V, you are in the forward direction and should reverse the connections to the diode.
If you measure close to 9 V, you have found the C-B diode, whose breakdown voltage should be larger than 9 V.
If you measure between 5 and 7 V, you have found the B-E diode, and are applying between 100 uA and 50 uA (with 40 k)--disconnect quickly.
Really old germanium transistors had BE breakdown voltages comparable to the CB breakdown, but virtually all planar silicon transistors have this low breakdown voltage as a feature.