For SLI matching, your best bet really is to get the model number and track it down by that.
There's too many variations to guess, and what you need is an exact twin. If you're savvy, you can try this:
The below steps require that the user first get to a MS-DOS prompt. Information about getting to a MS-DOS prompt can be found on document CHDOS.
At the C:\> prompt type the below commands.
debug <press enter>
At the - prompt type the below command.
d c000:0040
After typing the above command you should receive several lines of text similar to:
C000:0040 00 00 00 00 00 00 00 00 - 00 00 00 00 00 00 00 00 ................
C000:0050 E9 63 7B 00 B4 10 49 27 - E9 FE 2B E9 F7 2B 50 4D .c{...I'..+..+PM
C000:0060 49 44 58 00 5B 00 00 00 - 00 A0 00 B0 00 B8 00 C0 IDX.[...........
C000:0070 00 5B 53 54 42 20 6E 56 - 49 44 49 41 20 54 4E 54 .[STB nVIDIA TNT
C000:0080 20 76 65 72 2E 20 31 2E - 31 30 20 0D 0A 00 1B 43 ver. 1.10 ....C
C000:0090 6F 70 79 72 69 67 68 74 - 28 43 29 31 39 39 38 20 opyright(C)1998
C000:00A0 53 54 42 20 53 79 73 74 - 65 6D 73 20 49 6E 63 0D STB Systems Inc.
C000:00B0 0A 00 22 6C 2C 0A 01 00 - C3 50 24 7F E8 60 36 58 .."1,....P$..'6X
As you can pick out in the above dump this gives you enough information to determine the make and the year made on the video card. On line 4 you can see the make of this video card, which in this case is a nVIDIA TNT, which would be the Riva TNT chipset. The next line you notice the version of the card and finally the line thereafter is the copyright or the year manufactured generally.
If you are unable to capture any information that sounds like the video card you can also type
-d c000:0090
The above line will give you a dump similar to the above example however may have additional information about the video card.
Once you're ready to exit the debug prompt type quit to exit back to the MS-DOS prompt. If you wish to close the MS-DOS window type exit.
Good luck.