About all these "special commemorative" runs...
There's a zillion of them. OK, maybe I exaggerate.
There are a LOT of smaller size runs that have been made over the years, many for particular police departments, many to commemorate some event or other.
The thing to keep in mind is that if a pistol is stated to be a "special" piece, it probably not that special because anyone can do a run of any size and make a new declaration of rarety or specialty.
The REALLY rare guns are those that have fallen through the cracks and actually WERE a part of important history, or maybe some that were meant to be the beginning of a larger production run but were discontinued almost immediately, resulting in only a handful of that variant in existence.
Yes, most of these declared "special" variants might bring a little more than it's completely original counterpart, but often that's because the "special" gun was put away and is in almost new condition.
The bottom line is that the OP gun is worth AT LEAST what another 99% gun would be worth, and maybe some small change more, but that's usually it.
If you want to know the absolute honest truth of what that gun is worth, take some great pictures and put it up on Gunbroker.com as an auction.
An item isn't worth what someone "says" it's worth, it's worth what someone is actually willing to PAY for that item.
A GB auction in which thousands of gun enthusiasts, collectors, and profesionals get to have an opportunity to bid on it will tell you EXACTLY what it's worth.
If it brings $30,000, great, then that's what it's worth. But I think it would end up bringing in the $700 to $850 range (I'd be surprised if it brought that much), not so much that it's a State Dept. marked gun, but because of it's 99% condition and that it has it's original box and I will assume all the paperwork and cleaning brush etc. as well.
I have to say that I'm surprised that you found one in 99% because if that was an issue gun, it should show a lot of holster wear (which I personally think might make it even more interesting to a collector).
All that said, if I came across a 99% Model 19-5, I think I'd keep it and shoot it some but keep it well maintained.
Being a -5, it was probably made in the 80's, and so it's not a terribly old handgun from a historical standpoint anyway, and to me makes it a great shooter to use the way it was built to be used.