Terry - it's actually Dorian mode. That's the minor scale, but with a b7 (ascending as well as descending).
It's one of the Gregorian modes - on a keyboard, you pick any white key as the key, and you hit only the white keys as you go along. Dorian starts from D - but obviously you can play minor with a b7 in any key.
IIRC, this was from the system before they started adding black keys on organ keyboards. But it is a little confusing, because the first key to be added moved Bb away from its white key to add B natural. The Germans still call a B an H - and a B in German is what the rest of the world considers a Bb.