Comment by btrettel

In "traditional" engineering, there are a lot of old code bases still in use that few people (if any) have a solid understanding of. I've seen code comments dating to the 70s. Often the code was "documented" in internal reports. Many of these reports are now lost. These reports are often incomplete or unclear when they can be found. Plus, what you read in the ancient reports may not be current.

The job ad will probably not directly say anything about code archaeology. If the job ad mentions some sort of in-house simulation software, and the organization is 50+ years old, I'd say it's a coin toss as to whether you'll have to be this sort of software archaeologist from time to time.