Poster from Chemins de Fer Paris-Lyon-Méditerranée ('PLM') advertising the Simplon Orient Express. I don't have a date for it but from its style it is certainly pre-WWII and its display of the southern route via the Simplon Tunnel (hence the name) places it as post-1919 (that's when the tunnel opened).
The presence of a southern spur to Athens might imply a date after 1930 when the Arlberg Orient Express began operating although I have seen this poster dated as from 1922.
The map shows a variety of routes. Two (London - Paris- Dijon - Lausanne and Bordeaux - Lyon - Turin) meet at Milan. The service then passes through Venice and Trieste where a service heads north to Bucharest. The southern line goes via Belgrade to Nisch (Niš) where a route goes south to Salonika (Thessaloniki) and Athens while the main line goes via Sofia to Constantinople (now Istanbul).
The artist was Roger Broders who was commissioned by the PLM to design a number of posters.
Keywords: Chemins de Fer Paris-Lyon-Méditerranée ; PLM; Simplon Orient Express; Simplon Tunnel; Arlberg Orient Express; 1922; London - Paris- Dijon - Lausanne and Bordeaux - Lyon - Turin; Milan; Venice; Trieste; Bucharest; Belgrade; Nisch; Niš; Salonika ; Thessaloniki; Athens; Sofia; Constantinople; Istanbul; Roger Broders