Railway abbreviations have the following meaning

Railway Country Era Name of railway
KWStE Germany before 1922 I Königlich Württembergische Staatseisenbahn
Royal Württemberg State Railway
KBayStEB Germany before 1922 I Königlich Bayrische Staatseisenbahn
Royal Bavarian State Railway
KSStB Germany before 1922 I Königlich Sächsische Staatsbahn
Royal Saxon State Railway
KPEV Germany before 1922 I Königlich Preussischer Eisenbahn Verband
Royal Prussian Railway Union
DRG Germany before 1949 II Deutsche Reichsbahn Gesellschaft
Railway Company of the German Empire
DB Germany ( 1949-1990 III/IV Deutsche Bundesbahn (West Germany)
German Federal Railway
DR Germany  1949-1990 III/IV Deutsche Reichsbahn (East Germany)
Railway of the German Empire
DBAG Germany after 1990 V Deutsche Bahn AG (unified Germany)
Thalys Germany and France V Joint high-speed venture of DBAG and SNCF providing service from Cologne to Brussels, Amsterdam, and Paris