When did the GP-100 come out? The reason that I ask is because when I took my LFI class in Long Beach, California in 1985, Massad Ayoob let me dry-fire his Ruger and I want to say that it was a GP-100. It could have been a Security Six but I am thinking it was a GP-100. Anyway, my point is that Ayoob's Ruger had a very good trigger pull on it, so it wouldn't surprise me that yours has a good pull as well.
Anyway, congratulations on the purchase. I'm sure that you'll really enjoy it.
Seems like I read that the GP came out in '85.
Speaking of the trigger, I just finished polishing the internals and replacing the springs. Went with 10# on the hammer spring, and 8# on the trigger return spring. According to my cheap Wheeler gauge the DA pull is 6.5# and SA is 2#. No grit or hitches at all, and the reset feels good. I have some ammo arriving later today, and am hoping that it still functions 100% reliably. If not, I can always bump the spring weight up.
I have to say, with just a little work and $10 worth of springs I'm really impressed with the results. I'll have to post a review once I have some more rounds range.