This proprietary cartridge was designed by Keller & Simmann GmbH of Schwäbisch Hall, Germany (K&S) and cases were produced for them by SHM. This appears to be based on the old 6.5x52R Tesching (T76) rimmed case (25-35 WCF) base with a c10.6mm head and c12.8mm rim diameter, that was given some Ackley treatment. CIP approved in 2012 and by 2015, K&S were able to provide properly headstamped 6.5x52R K&S cases from SHM and available in 2 loads with an 8.4 g  (129 g) heavy Hornady SST and a lead-free 6.5 g  (100 g) heavy Barnes TTSX