Serial # tells me it was made in 1987, the next to last year of the Six's production.
Barrel length should actually be 2.74" 70mm, a standard factory size.
Grips are factory, made for Ruger by Siles I believe.
That's all I can tell ya.
One of the others here might be able to tell ya more, a call to Ruger might get ya the actual shipping date, model number etc.
Looks real nice, congrats.
Sal
PS, What did ya have to pay for it?