That should make a fine carry piece, nice pickup. The 2.5" model 66 wasn't introduced until around 1974 or '75. The serial should be a K prefix, most likely 5K-9K something if it is indeed an early no dash. BTW, I believe the hammer and trigger may have swapped out at some point as they appear to be case colored, instead of flash chromed; as they would have came from the factory. Just thought I'd share. All things considered, it should be a sweet shooting snub! Enjoy.