The author of this image from Liechtenstein is unknown, and the image was published at least 70 years ago. It is therefore in the public domain in Liechtenstein by virtue of Art. 34 of the Liechtenstein Copyright Act..
Note that this applies only if a reliable source is cited to indicate that the author is not publicly known; just not knowing who the author is is not enough to qualify the image as public domain. This image may not be in the public domain in countries other than Liechtenstein.