We get many people that want to purchase replacement parts for their iPhone 3G and iPhone 3GS but they do not know how to tell which model they have. Here is a quick way to figure out the model iPhone you have.
The iPhone 3G has a chrome apple logo and the letter for the word "iPhone" is white color.
The iPhone 3GS has a chrome apple logo also but the lettering for the word "iPhone" is also chrome to match the apple logo.
Hope this helps.