Thank you very much for your answer.
Am I right that Hakushū is the name and Shiromatsu (Shiramatsu) is the family name?
Do you have any ideas for the age of the scroll?
Any advice is very appreciated.
白松 is the name of the artist, and the reading of it would be one of the three; Hakushō or Shiromatsu or Shiramatsu. (Sorry, I meant Hakushō, not Hakushū, in my previous post.) Hakushō is a given name, and Shiromatsu / Shiramatsu can be both a given name and family name. It's impossible to figure out the correct reading only from the kanji.