Many bonsai people have other hobbies. Sometimes they combine those hobbies together such as collecting bonsai-related pins, phone cards etc. I collected stamps since I was a kid, and am interested in bonsai-related stamps and postal items. I also collect old bonsai and penjing postcards, preferably postally used.
Below are my Japanese postcards with bonsai in the pictures; they are about 100 years old and were hand-tinted. Strictly speaking, most of these postcards show Japanese woman activities with bonsai in the background. I have not seen postcard of that period with just bonsai as the main theme. Nevertheless, they allow us to see how Japanese bonsai looked like a hundred years ago.
Besides the date on the postcard, one can tell the card is pre-1907 by looking at its back, called an “undivided” back. The Japanese postal authority did not allow writing messages at the back of a postcard, just the address. The rule changed in 1907, a vertical line was added to the back, divided it into two sections; one for message, the other for address, like what we see in the present day postcards. Click this site to learn how to date pre-war Japanese postcards.
In the late 19th and early 20th centuries, Yokohama Nursery Co. exported bonsai and Japanese plants to Europe and the US. This is their advertising postcard from the 1915 Panama-Pacific International Exposition held in San Francisco. The Palace of Fine Art building from the Exposition still stands in the Marina bay area.