Your Model 29-3 dates to about 1987. Member Kernel Crittenden can probably narrow that down to month.

Production and Engineering Changes:
-2 (1962) Cylinder stop changed, eliminate trigger guard screw
-3 (1982) Eliminate cylinder counterbore and pinned barrel with small change in in cylinder length to 1.69"
-4 (1988) New yoke retention system/radius stud package/floating hand: early models marked 29-3E for endurance package.