Today in Postal History

This 5c. Swiss postal card was franked with the stamps of three other stamp issuing entities
and posted on board a vessel cruising Lake Constance (Bodensee)*
on the northeast border of Switzerland and Germany.
Someone has annotated the cover with Schiffsbrief (ship's letter).

It was put into the mail at Friedrichshafen a. Bodensee where it received four CDS strikes.
Its destination was Wuchow (now Wuzhou), China.
Wuchow is about 200 km west of Canton (Guangzhou)
which, in turn, is about 130 km inland from Hong Kong at the head of Zhujiang Kou bay.

En route to its destination, the postal card received a Singapore to Hong Kong maritime cancel
on August 12 and arrived in Wuchow on August 20.*

In the lower left there is a Bavaria 1888 3pf. green arms (Scott 59).
In the upper right there is an Austrian 1899 1h. lilac Franz Josef (Scott 70).
Finally, there is a Württemberg 1893 2pf. slate gray numeral (Scott 55).

Although this appears philatelic, I tend to believe that it was more likely
a souvenir prepared by a traveler or excursioner who was intrigued with the thought
that the stamps of four different administrations
were available for mail while cruising Lake Constance.
It appears to have been common practice to prepare such souvenir cards.
David reports having seen a number from this period  over the years.
Each of the stamp-issuing entities bordered Lake Constance.*
What do you think?

*Thanks to David Benson for reminding me of the facts concerning the countries adjacent to
Lake Constance, finding the link, correcting the maritime cancel, and expanding my thinking.
Amazing how much there is to learn about from these items!