this should be an Amati toneking. Contrary to some comments both German and Bohemian saxophones have been equipped with microtuners so the presence of this is not at all unusual on a saxophone made in czekoslovakia. I personally would hesitate calling any Amati a Keilwerth stencil even though there are clear indications of the continuous (to this day!) co-operation between the companies. I am personally very fond of certain Amatis namely the early Super Classic.
Having said all this, there is also little value in these horns. Even at the top of the market they were cheap and these days finding a buyer for these saxophones is very difficult because the money that you invest on a repad is actually more than the value market of a repadded saxophone.
When buying Amaty tonekings make sure that where the RG thumbrest is there is no (very small) H to be see because that is the sign, you've guessed it, of a high pitch horn which is , of course only usable as a decoration.