Rotbart 4S/5S. Info?

[il dottore]

I've found a couple Rotbart razors for sale. One has "4S" on the box, and looks like this:

(The guy selling it says it's in mint condition, which is a plain lie, but whatever.) The head looks the same as some other safety bar Rotbarts I've seen around here (including a beautiful one with black anodized handle), pretty modern-looking with a scalloped guard. How does it shave? Any other info on this model, production period, materials etc?
I've also seen another one for sale, "5S" on the box, but it's unopened so it's impossible to tell whether it's similar. Anyone have a clue?

 

[nemo]

It's a Rotbart No.15
Buy it, they shave like a dream, excellent head design.



The knob often is discolored to a dark shade.



Never been used, paper was removed only for the photo.

 

[il dottore]

Oh, nice! Are they always silver? Maybe that's what the "S" stands for... That would explain a lot (though not all, there are more photos) of what I thought was scuffs and dents.
Any idea if the 5S is the same, and production period? Reasonable price?