After reading over some Lisa technical docs, I finally came up with the answer to a Lisa question I had a while back. I found it pretty interesting, so I'm posting it here for any other Lisa collectors:
The issue at hand was how the Lisa "knew" its own serial number. Apparently, this information is coded into the Video State Machine ROM located at C6 on the CPU board.
Here's how to retrieve the serial number encoded into a Lisa's Video ROM:
Put your Lisa in Service Mode. When the memory is being tested, press the shift key. Then, try to boot up from a blank floppy drive, the Lisa will respond with an error. Then type Apple-S and you'll get to service mode. Click on "Display Mem". When prompted for "Address?", type 240, and click enter. When prompted for "Count?", type 20. You will then receive two lines of code.
First remove every other nibble like this:
00000240 0F0F 0002 0802 0002 0000 0400 0300 0F0F
240 F F 0 2 8 2 0 2 0 0 4 0 3 0 F F
Then group the numbers as follows:
Number of the Nibble in Hex 01 23 45 678 9ABC D EF
Address 240 FF 02 82 020 0403 0 FF
XX PP YY DDD SSSS X XX
Extract the serial number from this group of 16 nibbles as follows:
a. Ignore nibbles 0,1,D,E and F, marked as XX or X above.
b. Nibbles 2 and 3 are the two digit plant code (PP).
c. Nibbles 4 and 5 are the two digit year code (YY).
d. Nibbles 6, 7 and 8 are the day of the year code (DDD).
e. Nibbles 9 thru C are the 4 digit serial number (SSSS).
The Applenet Number is similarly embedded in the first 8 bytes of the next
line of the memory dump. So, using the same method as step 4 above, we get:
00000250 0000 0100 0004 0102 0002 0900 0000 0000
250 0 0 1 0 0 4 1 2 0 2 9 0 0 0 0 0
Number of the Nibble in Hex 012 34567 89ABCDEF
Address 250 001 00412 02900000
PPP NNNNN XXXXXXXX
7. To extract the Applenet Number:
a. Ignore nibbles 8 through F, marked as XXXXXXXX above.
b. Nibbles 0, 1 and 2 are the AppleNet prefix (PPP).
c. Nibbles 3 thru 7 are the AppleNet number (NNNNN).
I know it's not new information, but it's useful to know and have on hand. It's certainly useful when trying to tell if your Lisa has its original CPU board/Video ROM. In fact, I'm surprised more eBay Lisa sellers haven't shown a picture of these lines of code alongside the serial number sticker, to show that the parts are original.