iPod models

1. ipod touch 1g available in 8/ 16/ 32 GB. model number is A1213 ( model number is written on back side of ipod)

2. ipod touch 2g available in 8/ 16/ 32 GB model number is A1288 ( model number is written on back side of ipod)

(ipod touch 2g has two models. they are mb model and mc model) ..mb model released earlier and mc model was released with ipod touch 3g. some shop sell them saying it as 3g. But actually it is actually 2g ipod touch)

3. ipod touch 3g available in 32/ 64 GB model number is A1318 ( model number is written on back side of ipod)

4. ipod touch 4g available in 8/ 32/ 64 GB. model no is A1367 ( model number is written on back side of ipod)

( only 4g ipod touch has the camera function)

you can easily identify ipod by checking model number which is written on every ipod touch back side

you can check these two links to know more

http://support.apple.com/kb/ht1353

http://en.wikipedia.org/wiki/IPod