Looks odd indeed. Could be playwear, but the picture shows the top of the fingerboard so that would be kind of weird. Might also be just the neck finish though. The necks on these are lacquered right up to the edges of the fingerboard. Everything but the playing surface of the board is finished. Maybe the lacquer is just worn or shrunken.
On my 1983 MC924 the finish wore quite differently, it started chipping from the edges down. I had a luthier apply some new lacquer to stop the rest from doing the same, it's fine now. My 1981 MC924 is still practically as new.
