I have had the recent opportunity to dig inside a couple of 9100's lately (I bought a few NOS ones) and I kept one to go along with my old 9100. Now the problem with these suckers is the software is keyed to a serial number embedded in the EEPROM that is tucked away on the main PCB. It just so happens that this part (an Xicor X2444 - 32 bytes) is readable by my Xeltek Superpro programmer so I unsoldered the one in my old base and read it, and then tried it again in the original base. Still works. So then I decided to unsolder one from my keeper NOS 9100 and read it tonight. So what I have is two 32 byte data streams, the first one (old base) is serial number 4900002 (unknown Site Code) is: A2 C4 4A 00 42 03 FF FB 01 00 0A 00 03 50 08 40 00 00 00 00 00 03 00 00 FE 02 00 00 00 00 BF BE And serial number (NOS) 4775000 "Site Code 1" is: 58 DC 48 00 42 00 FC 00 FC 00 00 00 03 50 08 20 00 00 00 00 00 00 00 00 FE 02 01 00 00 00 23 0F The first 9100 has the following options: 4 megs of RAM installed Sony floppy Programmers option w/video card Version 4.X software? The NOS 9100 has 2 megs of RAM ? Floppy Version 4.1 software I'll dig out more from these using the utility disc this weekend. I think the "40" on the first row last byte is the RAM size, this makes sense as the second 9100's is only "20" (2 megs), I suspect the first three bytes are the serial number...maybe... I accidentally copied the Utilities disc to the old base and it has taken over the drive from the original operating system. If anyone has 9100 discs they can be archived and stored via TELEDISK (old DOS or W95/DOS) program...I'd like a copy for trying to figure this protection out for archiving. Fluke has completely dropped the 9100/9010 and sold off everything...the buyer was Shy at Navatek.com who is only too happy to help with parts etc... shy@navatek.com John :-#)#