I just got a full box of this LK-cases from RWS/Utendoerffer (from the markings from 1929) Fertigung/Making: Y47K
and here a Geco box, of 12,7x44R certainly made by RWS FOR Geco, as the FZ show. Its from 1935 as indicated by E51Q, Headstamp is only GECO .
Box and hs:
AND A PIC FROM AN OTHER GECO BOX (PIC ONLY RECEIVED BY MAIL); so, its not mine…FZ not known…
As this Rifle boxes using the RWS-Coding, and the Geco-pistol boxes are using an up to yet unknown code, it shows clearly that the rifle ammo was made for them by RWS/Utendoerffer, and vice - versa, means some pistol rounds where made by Geco for RWS with THEIR RWS-headstamp.