Leather Envelopes.

My sketch of how I think this leather envelope is secured.

It looks to me as though the envelope is double. First the letter is folded and placed in leather which is also folded. Then this leather is placed in the actual envelope and secured with a leather tie/thong. At this stage it looks as though these letters are then placed in another package which carries the postal address, as I can not see a way of addressing these leather envelopes. If I find more info I will update this post.

Images courtesy of: http://attentioncherie.blogspot.com/ and http://florizel.canalblog.com/