Mail Art from 1911 ?

Found at the todays fleemarket, 

an unusal sending from the year 1911, 

sent from the Netherlands to Germany

tiny wooden shoes on a postage label with postage stamp from Dedemsvaart

Mail Art from the year 1947, done by Jürgen Schrader ... PART 7

 envelope from the 28th of march 1947, with one further illustration inside

Mail Art from the year 1947, done by Jürgen Schrader ... PART 6

envelope from the 10th of march 1947, with further illustrations inside

self portrait ... he mentioned it inside the letter

Mail Art from the year 1947, done by Jürgen Schrader ... PART 5

envelope from the 3rd of march 1947, with two further illustrations inside

Mail Art from the year 1947, done by Jürgen Schrader ... PART 4

envelope from the 25th of february 1947 with two illustrations inside, letter is missing

Mail Art from the year 1947, done by Jürgen Schrader ... PART 3

Mail Art or not?

this enveope is from the 18th of february 1947

Mail Art from the year 1947, done by Jürgen Schrader ... PART 2

here the second envelope from the 17th of february 1947
inside also another drawing and a letter to his family, which I will not post here.
Mail Art or not?

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.