I think that's a video cable for an Amiga monitor? Question is which one.
That's not a DB-25 -- if I'm counting right, there are only 23 pins (which means it isn't quite a B-sized D subminiature shell).
But, the male DE-9 sure looks like what you might see outputting video for the 80-column mode on a 128.
You've got a real oddball there, that's for sure.