Student was a designation used in the 1970s & 80s by Keilwerth. It was replaced by the ST90 in 1990. 

Keilwerth didn't really focus a great deal on student horns, and primarily outsourced their production.

According to German saxophone historian, Uwe Ladwig, JK had their simple student horns built by: Rampone & Cazzani, Amati*, B&S, Amati* again, and most recently Jupiter. (p. 166 Saxofone: Ein Kompendium)

*Note Amati horns were stamped with Amati serial #s.

The horns I placed in this gallery are the ones built by Amati. Check that gallery as well for more obvious Amati stencils.