Every new form of communication eventually evolves to include sexual content  -you might be amazed to know how much internet traffic is related to pornography.

This was true of postcard communication, also.

It is not hard to find individual postcards of near-naked bodies or postcard sequences depicting the undressing of a young woman.

In the late 19th century, several French publishers specialized in the production of nude images on postcard stock, and “French Postcard” became a generic name for the racy postcard.

The production of risque postcards occurred in many nations, however.

https://en.wikipedia.org/wiki/French_postcard

I believe that this single postcard may have been part of a set -earlier postcards would show the woman removing her shoe, her long stockings, unbuttoning her blouse, taking off her skirt, etc.

The final postcard is probably a bare-breasted figure seated in the bath.

This postcard was not mailed (postal regulations may have forbidden it).

It lacks any identification of the collector, although I have found some nude images that do have the owner’s name attached.

One hopes that the postcard provided aesthetic satisfaction to the collector of the early twentieth century!