Without photos, and accepting a range of what might be called "really clean" I'd say your guns' FMV is somewheres $1000 to $1400/$1500. I own a really clean 4" 617-4 myself that I've considered selling on and off, and have viewed quite a few comparable auction sales.
The 617-4 was only made for some months before the lock showed up, so not only is it the only 10-shot prelock 617 ever made w/ a steel cylinder, it's also not very common.
Your 4" is also worth well more than a comparable 6" 617-4, I suspect cuz the 6" (used to own one) weighs about a ton....