device:
iPhone 3GS with OS 5.1
Download iOS 5.1 (9B176) Firmware for iPhone 3GS | iOSIndex
specs:
Amazon.com: Apple iPod touch 32GB Black (4th Generation) (Discontinued by Manufacturer): MP3 Players & Accessories

name of firmware= 6.1.3 (10B329) iPhone2,1_6.1.3_10B329_Restore.ipsw