Is one version of 10.5 the same as the next?

I'm thinking of purchasing mac OS X 10.5 from a private seller. The seller tells me that the OS came with a 20" silver intel imac, but he's asking me to make sure it's compatible with my mac (macbook, 1.83Ghz, 2 gig ram, 200 gig hd, superdrive). I would have thought one version of mac os was the same as the next, but he seems to think the version he is selling is specific to his mac. Can anyone confirm as to whether it will install on my machine without any problems?

The DVD of OSX that comes with a Mac Model like say the iMac is made for that machine. It will work on other iMacs that are the exact same model, but not on any other Mac. If it came with his iMac 20" Silver, it is worthless to you for your Macbook. You need the Black OSX 10.5 Leopard DVD which is the full retail.