Mathilde Lukacs, née Herzl, the eldest sister of Elisabeth Grünbaum, was married to the jeweller Sigmund Lukacs (1877–1971) from Bátaszék, Hungary, who partnered Mathilde's brother Maximilian Herzl (1878–1946) in the business of her father, Bernhard Herzl (1842–1915). Sigmund Lukacs also had his own general store from 1907, moving in 1917 to their home address at Rudolfsplatz 3 in Vienna's 1st district. Mathilde Lukacs was the Prokurist (authorized signatory). Directly after the annexation on 14 March 1938, Sigmund Lukacs was arrested by the SA but was released soon afterwards after he had undertaken to leave the country within a few weeks. When he reported to the Jewish Community (IKG) emigration department in May 1938, Max Herzl had already intervened from Antwerp to arrange a visa for Belgium, initially for three months, for his sister Mathilde and his brother-in-law Sigmund Lukacs. The Lukacses then applied to the Zentralstelle für Denkmalschutz (Central Monument Protection Office) for authorization to export sixty art items, including porcelain and carpets. On 12 August 1938, Sigmund und Mathilde Lukacs deregistered from Vienna and two days later their removal goods and art collection left the German Reich. From 26 August 1938 to 25 January 1941 they lived in Antwerp, then in Brussels, where they were arrested on 26 October and obliged to move ("résidence force") to an old people's home in Anderlecht. From October 1944, Mathilde and Sigmund Lukacs lived at 13, avenue Hortensias in Brussels, renamed avenue Général Eisenhower after the city was liberated. During the following years they became friendly with the sociologist Ernst Federn, who knew Fritz Grünbaum from their time in Buchenwald concentration camp and had gone to Brussels after being liberated, where Mathilde Lukacs took a motherly interest in him. The Lukacses returned to Vienna for the first time after the war in 1948.
Mathilde Lukacs first submitted a missing person announcement to the International Committee of the Red Cross (ICRC) for her sister Lilly Grünbaum, who had already been murdered in 1942, in February 1944, when she herself was still in danger. She continued searching in the 1950s and 1960s with ITS Arolsen, the ICRC and the IKG Vienna. Mathilde Lukacs is of interest in terms of provenance research because between 1952 and 1956 she sold 113 works from the art collection of her brother-in-law Fritz Grünbaum, who had died in a concentration camp, to Galerie Kornfeld in Bern, Switzerland. In autumn 1956, the gallery organized a Schiele sales exhibition in which three oil paintings and fifty watercolours and drawings from the former Grünbaum collection were shown – according to Eberhard Kornfeld "the first major manifestation for Egon Schiele after 1945", which formed "the basis for the rapid increase in value" of his works, which still has an impact on the art market today. The former Albertina director Otto Benesch wrote the foreword to the depot and exhibition catalogue. This exhibition marked the end of the business relationship between Mathilde Lukacs and Eberhard Kornfeld. The precise manner in which she acquired the artworks is unknown. When she sold them in the 1950s, she had not been designated by the court as the legal heir to the collection or to Fritz Grünbaum's estate. Her application on June 1954 to have her sister declared dead was withdrawn a short time later without reason. The Lukacses returned to Vienna in 1960, where they lived until their death – Sigmund in 1971 and Mathilde in 1979 – in a Wiener Kaufmannschaft home at Hartäckerstraße 45 in the 18th district. Mathilde's estate, consisting solely of jewellery, was declared heirless and transferred to the Republic of Austria after the deadline for convoking unknown heirs had expired.