The 6n23 Voshkod Rockets have a very unique upside down "flying saucer" getter. I have never seen a getter like that in any other tube. They are also made of exceptionally thick glass and are quite heavy. The "Rocket" logo on mine is almost imperceptible. You have to look at them under a strong light.
Stay away from the Russian Reflectors with a blue 'OTK' stamp - they suck. Also for any of the 6n1s.