Mail Art from the year 1947, done by Jürgen Schrader ... PART 1

Today I bought some envelopes, done by Jürgen Schrader who lived in Hamburg in a hospital in the year 1947 and he has sent some letters to his family living in Berlin. In the next days I will post them to the blog as a little history in Mail Art. Jürgen is getting more and more courage decorating his envelope, the first is only decorated backsides, but the next will show more and more decoration on the front side. Feel free to give comments on this envelopes, is it Mail Art or not?
here the first envelope from the 11th of february 1947
inside also a letter to his family, which I will not post here.