1968 - 1988.
The Ruger web site has sn data if you can get to it.
To determine the age of a Ruger Single Six with the serial number 61-10765, you can refer to Ruger's serial number records. Based on those records, this particular model was manufactured in the year 1961. Therefore, as of 2023, the Ruger Single Six would be 62 years old.
Revolver
Have the model and serial number of your firearm handy, and call Ruger @ 603-865-2442, and they will reply (usually within a week) with the month and year your firearm was manufactured.
Model numbers 117 vs 207 and external physical features
In stainless, and in New in Box (NIB) a Ruger Speed-Six in 9x19 is worth $1,000+ as of 2010. In stainless, and in like-new condition, a Ruger Speed-Six in 9x19 is worth $700+ as of 2010. The 9x19 version of the Speed-Six is quite rare in the U.S. since only a few were sold in the US from European and Israeli military/security contract overruns.
Yes
1960 according to the Ruger website.
75-260 or so
If the ruger site is up, it has sn data on it.
If you can access the Ruger web site, sn data is posted.
Ruger has sn data on its web site