The first generation iPhone was released in 2007 so the device you're talking about would have been at most 5 years old at the time. Nevertheless that's still considered extremely old for a modern device.

(For reference, my current device is a 4 year old iPhone 5S because I like the form factor, and it still does what I need. It's just about getting to the point where I'd like to upgrade it, but that's mainly because I keep running out of storage space.)