Yeah, mine were welded closed (kept the trim) but the when they are the recess usually remains. It would take a bit of work to get it that smooth.
Yeah, pre-'71 is right but those vents are often welded closed too which isn't a bad thing because they're only rust traps.
Are you buying Tim?
Still though, if it is only surface rust as your man says and it runs, it could be a nice cheap early T25 for someone and they're getting rare now!