address stamp on barrel

At what point in time did the Ruger address barrel stamp change from Conn to NH ?
My older Rugers are Conn while the newer models are stamped NH.
thank you

Which Model?
Different changes came about at different times.

Redhawks, New Model Blackhawks and M77Mk2s are the models I am curous about
thanks for the response

Well, you didn't say which Blackhawk you were interested in,, so here is what I have so far.
According to the RENE Guide, the 357 had a rollmark change around serial number of 37-94649, which was in 2008. It also appears that most of the SA line went to Newport in 2008.
The Redhawks by somewhere around 503-59759 which was in 2009.
As for the M77 MKII's,, there are pages & pages of so many variations of these guns, that my skimming over them, I wasn't able to find a timeframe for them.

The Newport address probably went on the M77 Mark II sometime after the last revision to the Ruger Reference which was 2010. I remember noting the change, but would need to look through some old issues of RENE to pinpoint it.
Chet15