Help me date my S&W please

a) caliber - 22lr
b) bbl length - 4inches
c) grips shape - Sqaure, I took off the grips to verify. When I took off the grips I noticed the coil spring.
d) number of shots/cylinder bores - 6 shot recessed.
e) type of sights. - micro rear, ramp front pinned.
f) serial number - M420XX
g) Model number if it is under the crane. - 34 (no dash)
The photo does not due this gun any justice. This little revo is in great shape. It looks like it was a safe queen with very little shooting and everything is very tight.

I did try the sticky but most of the 34 info was generic or was 34-1 specific. I'm hoping to get specifics about my particular gun. From what I can tell it looks like a transition between 1968-69 or 69-70.