Look at the price of this Single Six. What year do you think this was bought. This has been in the family for a while. Also has both cylinders .22 Mag and .22 LR.
If the guns owners manual is in the box, it will have a printing date. The package had to be assembled after that date and put you in the ball park. If not, try the Link. They talk about several different boxes by color of box, color of printing and what handguns were normally packaged in them.
I’m guessing around 1975. My cousin bought one around then and that’s about the price he paid.
It’s for sure not before 1973 because the box says New Model and 1973 is when the New Model came out. The New Model has the transfer bar mechanism.