It's a Model One, 2nd issue, handsome looking gun, congrats.
Silver on the brass frame is a standard finish, and it will indeed tarnish darker & darker to almost black over the years. I'd strong suggest you not wipe off any more tarnish, that dimishes collector's value & the authentic appearance of your gun.
It's impossible to guess from photos, but if I had to, I'd suspect the barrel & cylinder might have started as blue, and now have lost their finish to a gray patina. You might find traces of original blue in protected areas if you look (bottom of barrel behind ejector stud for example).
IF it does indeed have most silver & little blue left, we might guess it as a 50% gun, which, if the gray metal is not pitted badly, could rate as "Fine" under NRA antique standards.
In SCSW we estimate the value of a No. 1, 2nd issue in Fine condition at $500.
You could also look at my for sale listings on my
www.ArmchairGunShow.com website & see what I'm asking for comparable guns. Here's a link directly to the listings:
http://armchairgunshow.com/otsDSA_SW_tipups.htm
I see 1st 2nds there as follows:
* Rare early square plate, Fine, $1,350
* Rare 2nd Quality, Mixed, $525
* Standard model (like yours), Fine $450
* Standard model, Fine +, $885
* Std., ivories, Fine, $650
* Unusual mkg., Fine, $540
* Std., about Exc., $750
* Std., mixed, $185
It's important not to confuse Model One, Second Issues with Model One, First Issue, Second Types.
The Mod. 1 2nd Issue brings the values above.
The very rare Mod. 1, 1st Issue, 2nd Type can bring values in the $5,000 to $10,000 range (or more or less depending on condition).
General info on identifying various S&W tip-ups is on my website here:
http://armchairgunshow.com/SWTU-info.html
More detailed info can be found in the Jinks, Neal & Jinks, or Nahas & me books.
Hope that helps. -- Jim
