Horta, Brussels, sells on 17 October 2016 a "J. Doré, French School" landscape, estimated at 500 to 700 Euro.
The signature to me looked closer to a G than a J, so I first thought of Gustave Doré, the famous illustrator (one of the best ever) who als painted landscapes, but his signature is different and his landscapes somewhat more conservative (the one for sale has more Van Gogh-like clouds, which Gustave would never do).
Looking further for possible matches brought me to Jacques Doré (1861-1929), less famous and valuable but still interesting.
Biographie Coloniale Belge"; born in Antwerp, died in Halle, worked in Belgian Congo from late 1891 until 1892 (catching hepatitis, which was still a relatively happy end as most of his co-travelers died). Lived at the Canaries in 1892-1893, then returned to Belgium where he lived as an artist (mainly landscapes). His health never fully recovered, he died in 1929.
I guess, with a name attached to it, it might make 1,000 Euro, but anything beyond that would be a surprise.
UPDATE: sold for 460 Euro, a bit less than I expected.