I've seen the same one be 'sold' three times over on eBay recently. It's on there now. There was a thread on SOTW about them a little while ago. It's a Dutch brand, often with rolled tone holes. In the SOTW thread, Milandro, who occasionally posts here (and also Dutch, so might have some decent local knowledge) was less than complementary. If memory serves me right he'd tried two, one was just OK, the other awful. Go carefully - there's probably a good reason why they are rare, no-body bought them!
I have two Shenkelaars saxes. One soprano from early 50's with rolled toneholes and an alto from the 50-60's. I think the soprano is made by Keilwerth Nauheim and the alto looks like a Weltklang. The Shenkelaars company was pretty succesful in selling saxes. They sold saxes under the Schenkelaars brand in the late 70's here in Sweden. The late Schenkelaars saxes was a West European sax.
Are the Schenkelaars saxes any good?? I think they are ok. My father (semi-pro) played the Schenkelaars in the 50's and 60's. He played "danceable jazz" and standard songs and the saxes served him well.
Schenkelaars was a company that made their own saxophones in a very distant past, then they started assembling from Keilwerth parts then sold stencils with their names made by a number of makers among other Weltklang/B&S and Orsi.
The Schenkelars which they made themselves were by far the worst western made saxophone that I have ever seen in my life and I remember the time that I saw one where the rolled toneholes looked just like someone had, badly, soldered a metal rim on a straight tonehole (I have seen this twice).
If you find a Schenkelaar that is a sure Keilwerth, buy it because it will be dead cheap (but old Keilwerths are not too expensive or difficult to find where I live!),I would personally leave any other one alone.
Actually , as one would guess, they are very common over here but due to the mix of quality of these horns they tend to be avoided by most. The Keilwerth stencils are pretty good but, since the " real" thing is rather plentiful too, why would anyone bother to buy a Schenkelaars unless it is very cheap? In any case the baritones seem to have a better than most record. A few days ago a Dutch sax collector was telling me that they at Schenkelaars also bought from Gubana of Timisoara Rumania. He was very derogative about these horns. I have actually seen some very beautiful art deco Gubanal ( cannot vouch for their sound because I haven't played any) heavily silver plated which looked absolutely stunning but my guess is that this was not the case with this other particular stencil.