Allen Loebl

"LOEBL was LOHSE's adviser and intermediary in a substantial number of transactions, and "spotted" pictures for him" 
https://www.dfs.ny.gov/consumer/holocaust/history_art_looting_restitution/The%20Allies/OSS%20and%20the%20ALIU/ALIU%20Reports/bruno_lohse.pdf

Who Was Allen Loebl? (Also: Ali Loebl) What was his role at Galerie Kleinberger in Paris? What was his relationship with Harry G. Sperling at F. Kleinberger & Co. in New York? What were his relations with the Nazi and SS ERR art looter Bruno Lohse? Why did he appear so many times on the Art Looting Investigation Unit Red Flag list?

Art Provenance Research Red Flags: Alexander Ball

Art Looting Investigation Unit Detailed Interrogation Report of Karl Haberstock (DIR 13) on refugee art dealer Alexander Ball "The implications of such a revelation are exceedingly grave, and BALL should be brought to account." However Alexander Ball and his brother Richard had already reached America.
source: War Department Strategic Services Report DIR 13
https://dfs.ny.gov/consumer/holocaust/history_art_looting_restitution/The%20Allies/OSS%20and%20the%20ALIU/ALIU%20Reports/karl_haberstock.pdf

Alexander Ball, also known as Alex Ball, A. Ball, A & R Ball, and Ball Galleries, was a Berlin art dealer who became a refugee and, unfortunately, worked closely with notorious Nazi art looter Karl Haberstock, helping him to locate Jewish collections for spoliation.

A Ball's activities are documented by the Art Looting Investigation Unit in several reports, including the Final Report Red Flag List of Names and the Detailed Interrogation Report (DIR) Number 13 of Karl Haberstock.

It is noteworthy how poorly Alexander Ball is documented and referenced today in art history dictionaries, encyclopedias, and art reference databases.

Art that passed through his hands landed in major museums. Any provenance or ownership history that contains his name in any of its forms deserves a closer look, with special scrutiny for items listed on the Nazi Era Internet Portal and items with gaps or other red flags in their provenance.

Below are a few mentions of Alexander Ball in historical sources as well as a few references for him.

Art Looting Investigation Unit Red Flag List of Names

Ball, Alexander. Paris, 9 rue Royale Aix en Provence New York (?). German Jewish refugee dealer. Intermediary for Haberstock in the sale of pictures from the unoccupied zone. Also believed to have informed on the whereabouts of prominent Jews, notably Guy de Rothschild. Believed to be in the United States.

de Beauperthuys, Simone le. Paris, 6 ave de la Grande Armee. Secretary of Alexander Ball and intermediary for Ball with Haberstock, to whom she offered pictures of doubtful origin. Also represented Fischer, for whom she signed a receipt to Bornheim in Paris, July 4 1941.