I could be wrong but I don’t think w113’s were delivered with stereo radios prior to 1969. The Becker Europa stereo was the only stereo available as an option. If ordered, speakers were installed in the foot wells which had openings for their installation. I have seen both Becker and Blaupunkt speakers installed as yours are or horizontally on the rear shelf. Some were dealer installed, while others were done so by the owners or by an audio dealer. Either way, they never looked like they belonged. Were it my car, I’d be tempted to follow your suggestion: remove them and patch the holes in the carpeting.