The GX1 had the following things of interest to me:

F000:B5DC B5E8 = "Optiplex GX1" -Could be useful for autodetecting model.
F000:B622 B626 = 5 Digit Service Tag

The GXi had:

F000:C192 C1A7 = "Optiplex GXi" =Could be useful for autodetecting model.

Unfortunately I could not find the service tag anywhere in the dump from the GXi. I don't know if this means it is not stored in the ROM of GXi's or if I was just not looking in the correct ranges.

Debug is a utility built into DOS (and NT) that is useful for running short Assembly segments, but can also be used to dump data from memory. To use it just type debug at the command prompt and you will be given a new prompt. Type ? for a list of commands. If you type "d F000:0 FFFF" you will be given a memory dump from F000:0000 to F000:FFFF. (This may take a while, debug is slow).

Mark