Very solid find at a hellof'a price! I saw a very similar Cobra from the 70's at a shop for right around $500, and thought THAT was worth the money.
By chance, did you check the timing? By that I mean, when you slowly...AND I MEAN SLOWLY!, cock back the hammer, does the drum fully rotate, or is there a final "click" when you check to see if it's all the way rotated?