Upgrades don't exist. There are no upgrades. Repeat after me. It cannot be an upgrade.
If you bought a Mac and it came with a drop in, use it on that Mac. If you bought another copy, use it elsewhere. But that other copy must be a full retail version (Edu or Dev or whatever) since there are no "upgrade" copies. And unless you buy a new Mac that comes with Leopard preinstalled (not a drop in) then any copy will work on any machine, they are not model specific. The only model specific disks are that ones that come with a new Machine to restore the OS and bundled applications to their original state at time of shipping.