Well, there is only "iPhone" in the back, so I presume original iPhone, right ?
1. Original Iphone - metal back with black plastic at the lower section.
2. Iphone 3G - black or white back, the Chrome Apple logo on the upper section, normal printed words at the lower section.
3. Iphone 3GS - Black or white bac, Both Apple logo & wording at the lower section are in chrome.
4. Iphone 4/4S - black or white with glass in the back
A1303 (weird, if I put only "A1303", preview translates first char in lower, this comment will keep it in upper)
You have a 3GS phone. So, if you hook it up to Itunes and do update, it will update your phone to 5.0.1. However, Apple still sign 4.1, so you can upgrade your phone to 4.1 only if you don't want to go to 5.0.1
Ok. Started download of both 4.1.0 ipsw from iClarified while waiting. Is this article still valid to follow to update ? http://www.ehow.com/how_7332585_roll-iphone-previous-update.html