[codefox1]

Yes, often QC marks, initials, stamps, etc... made on sets. Chalk marks in cabinets, etc. Initials, dates and stickers of repairmen of yore also common and should be preserved if possible, at least take a picture, print it and stuff it into the cabinet along with your notes if you care about those things surviving.

Some even put dots of paint on connections to signify inspection. Every Schulmerich amp and many altecs that I have worked on and other sets as well have those landmarks. You have to be very clever to hide a repair on some of these sets. Nail polish works for the dots, bare solder joints will tarnish in a year or so and match the others in a year or so, there are a million other things that can be done.