Since you care for the seat, I would take it off, box it, and store it for the next owner. That old stitching will probably start coming apart anyway. Save it in good condition for the next collector.
My personal preference for an upright style bike is an older Brooks B72. I bought a brand new one, but I think they changed the shape at some point. It's just not as comfortable as the older ones.
BTW: I have one of those Efkade seats also. It came on a 1960-61 Continental tourist. I have it boxed up and sitting on a shelf for the next guy.