Even ca. 1975 was early enough that the music score building programs available didn't have a lot of the automatic features common now - and the few that were around were really hard to obtain for an "independent" publisher.

The major music publishing houses had $10K programs that were (and still are) capable, but a smaller publisher might have used one of those "cluge" programs that required coding the print in a script and hoping the result would be what you intended. (No WYSISYG) A proficient compositor could do great stuff that way, but anyone without a lot of experience would be likely to get a few misplaced glyphs.

In that era, one of the best "cheap" methods was to lay out a score in a graphics program, like photoshop or even early AutoCadd, and position the symbols by hand. Of course, if you were a small producer you had to create the glyphs before you could place them, since music font handling was primitive in those kinds of programs.

Paper and Paste methods, with photo plates made with a big camera, were still fairly common.

With any of these methods, an error in placement of a single splat on one line would be fairly easy. Most current programs would make it very difficult if for some reason you wanted to do it. (I can't imagine what the reason would be.)

The errant "key signature" makes no musical sense to me, or according to any of my standard notation sources. (Gardner Read, Music Notation, Taplinger Publishing, ISBN 0-8008-5435-5, about $25, is the "Bible") I'm afraid, other than assuming it was a "typo," most musicians would have to have a long discussion to decide how to treat it, if it's something intentional.

The obvious: Can you ask the publisher?
The less obvious: Does anything show on a recorded performance?

John