The stamp is showing a view from the Mittenwald Viaduct / Mittelwald village (Germany) towards the summits of the Erlspitz Range. The Erlspitz Range is a subrange of the Karwendel Range. Mittenwald is situated very close to the German-Austrian border. All summits of the stamp above are situated within Austria.
The Mittenwald Railway connects the city of Innsbruck (Austria) with Garmisch-Partenkirchen (Germany).
The picture of the stamp looks similar to an old historic postcard of Mittenwald.
(please see below)