And no hint of a signature? It seems to me that all these drawings were made, for example, in some resorts may be for scientists, or some other vacation spot. And the headgear to be appropriate, and beards
, and the date - June. The absence of names of models suggests that they were so well-known author that the transcript is not required. By the way, the lack of signatures might be said that the author did not intend to present them, and, perhaps, did preliminary sketches for some kind of group portrait (eg, employees of any institution or academy).