Originally Posted by cbw
I'll show my ignorance, cause I probably should be able to tell by looking at it, or by it's age, single action? Nice Peace!
You can tell by looking if its double action or single action. Notice the position of the trigger in the guard, with the hammer down. The trigger will be at about mid-position for a double action, further back in the trigger guard for a single action.
Note the trigger position on this Model 29 (double action):
And, on this single action Colt:
Maybe so far more than you wanted to know. I tend to get preachy in my old age.