Interesting thread here
In my collection ofr postcards, I have about 10 leather postcards. Some collectors say they are more of an oddity really.
Some years ago, there was a collector at a stamp club I used to be a member of (club no longer exists now) and he showed me a postcard that was sent through the mail that was made of Birch bark. I am told that they exist in fewer numbers than their leather counterparts.
I also once heard that the designs on leather postcards were supposed to be unique. However, after looking at the postings here I am inclined to say that this is not the case. In my collection I have a leather postcard that has the same design as the "Drop Me A Line" illustration that KGV has scanned for us. I wish I could find it so that I could scan it here in case there are some minor variations. I think it is in that famous 'safe place' in my metal filing cabinets

I am not sure what the cut off date here was in Canada with the postal authorities calling a halt to accept these in the mail. Maybe some other SCF member can provide us with that information??
Happy collecting
Bujutsu