iphone with gps and no 3g

I have an iphone that I purchased from an individual. It was unlocked and jailbroken so I inserted my SIM card and everything worked. I was told it was 2G. After I started using it, I discovered it had GPS and was accessing the 3G network. After a couple of days, it would no longer access the 3G network (Edge instead) but the GPS continues to work. Since AT&T is my carrier, I restored the iphone using itunes. I then went online and changed my data plan from the $15 standard to the $20 iphone plan. All that process worked fine and of course the phone is now locked, unjailbroken, and legal. The other three things I should mention is that my serial number is printed on the back of my phone which I understand is indicative of a 2G, my serial number begins with 5K which I understand is indicative of a refurbished phone, and there is no menu item to turn on or off the 3G feature. The phone works fine and I am entirely happy with it but having the inquisitive mind that I do, I am curious as to exactly what it is I have. Thanks in advance for any help I can get.

Is the back of the phone aluminum or black plastic? If it's the former, then you have a first gen iPhone. If you have the latter, then you have a second generation, iPhone 3G.

It is silver which I know is first generation. What really puzzles me is that it was accessing the 3g network for the first couple of days I used it. I believe the previous owner was using TMobile and I am AT&T. Also, it appears to have the GPS functionality which I thought the first generation did not have.

Thanks

If it's first gen, then you are mistaken about it accessing the 3G network and it having GPS. Just because you have Google Maps and that it can somewhat pick up your position does not mean you have GPS.

The first gen does not have have GPS, but uses the phone towers to triangulate your position. It actually works pretty good. Some areas where I use it , it can only approximate my location, but overall it's not bad as a gps type device. It can track me driving down the highway fairly good. Have not felt any urgent need to go upgrade to the 3G.

If you say you were accessing 3G because it said you were in the top corner of the screen, this could be because once you jailbreak the phone you can have it say anything you want up there...

Agreed with Kash. What you are seeing is Google Maps. If it were really GPS trust me, you would know. DEAD on everywhere I have tried it. It even shows my house the exact distance from the street. Also on my AT&T plan if I check history it shows GPS on my bill with a small cost for using it. Just saw that last night.