Impressionist old mountain landscape painting signed Oppler

Oil on canvas board painting of a stark mountain peak and trees, signed lower right "Oppler". The 12" by 16" piece, unframed, appears to be painted on a later-than-1920's board of American origin, which makes me hesitant about calling this a work by the German artist Ernst Oppler (1867-1929), and there is no evidence that he visited the United States. A work online signed Oppler on a similar canvas board is stamped with a New York supplier address, adding evidence that this is not a work painted in Germany by Ernst Oppler. It is nevertheless an attractive mountain landscape, which would benefit from a cleaning as there is considerable soiling, especially directly above the mountain's peak. At upper right there is an area of tiny pinholes.