Great video as usual!
And what a coincidence! Would you guys believe that my company were about to throw away not one, but TWO 3457A (together with a bunch of other meters, counters, supplies, etc) some month before Christmas?! The production unit had determined to clean the shelfes from not-in-use-anymore...Luckily the larm went off, and a squad from the electronics department hurried down the stairs to the electronics waste area and "cleaned the table" so to speak. I got my hands on one of the 3457A's, together with a pair of Princeton Applied Reasearch 186A lock-in amplifiers, an hp3438A 3 1/2 digit bench DMM along with some more stuff.
This 3457A has Sno 3114A13573, probably manufactured spring-summer '92 (some date codes 9213). The "analog main board" is still basically the same, but there are some minor changes.
The opto coupler pairs are replaced with some hp device marked 901 366 (could not find this type designator), DIP-8 part. (No, it's not HCPL-901, that's a 16pin part.)
Oddly, the broken wire at the cut in the board by the optocouplers is still there, with the 1k resistor in place. Don't get the meaning if that? Anybody knows why the 1k + broken wire is good for?
The ROM sticker says Rev 2, but the part number's the same. The backup battery is Panasonic Lithium cell measuring 3.38V, probably replaced at least once. Otherwise it mostly looks the same as Dave's.