Af­ter a long pe­ri­od in which the sub­ject was ta­boo, an in­creas­ing num­ber of mu­se­ums are open­ing up to a trans­par­ent ac­count­ing of coun­ter­feit works, exchang­ing in­sights, and, if ne­ces­sary, de­cid­ing to write off works from their col­lec­tions. With a stu­dio ex­hi­bi­tion on the Rus­sian avant- garde, the Mu­se­um Lud­wig is ask­ing ques­tions about the au­then­tic­i­ty of works in its col­lec­tion. Thanks to Peter and Irene Lud­wig, in ad­di­tion to Pop Art and Pi­cas­so, the Rus­sian avant-garde is one of the fo­cus­es of the mu­se­um’s col­lec­tion, with more than 600 works from the pe­ri­od be­tween 1905 and 1930, in­clud­ing some 100 paint­in­gs.