Having found the name with a cross-research of the orders displayed on the portrait, it was also possible to know something more.
Feldmarschall-Lieutenant Joseph Weigl Frhr. von Löwenwarth served with distinction for 58 years in the Austrian Army, participated to more than 200 actions in front of the enemy, since the siège of Belgrade (as a Lieutenant in IR Kheul) under Marshal Laudon. He was also promoted to the rank of Major ("ausser seiner Tour") for war merits after the battle of Lonato (Italy), where he was also seriously wounded. His military "glory" reached its top during the 1814 campaign, at the surrounding of Besançon on 31st March-1st April, where under the eyes of Prinz Aloys Liechtenstein, Gen. Weigl displayed exceptional valour, leading his troops in a critical situation. With a "Handbillet" from Dijon, April 2nd, 1814, Emperor Franz I awarded him the Knight's Cross of the MMThO; some months later he received the title of Freiherr. Weigl died on 28th February, 1830 at the age of 83, while being Divisionär in Brescia. (notes from Hirtenfeld "Der Militär-Maria.Theresien-Orden und seine Mitglieder", Vienna, 1857, vol II, pages 1307-1308). He was still present in the "Militär-Schematismus des österreichischen Kaiserthumes" of 1830 as "Zweyter Inhaber" of Böhmisches Infanterie-Regiment 42.
Best wishes,
Elmar Lang