Postcard 8: Mainz mit Mainspitze

Today I decided to gather information about Postcard 8, a German postcard.
At the back of the card:

Mainz mit Mainspitze
Aufnahme von Rolf Kellner, Karlsruhe i. B.

After doing some research, I found out that Mainz is a German city located on the river Rhine while the Mainspitze triangle is a narrow piece of land between the Main and Rhine, where the photo must have been taken. Aufnahme von Rolf Kellner, Karlsruhe i. B. must have been the manufacturer of the card because Google search returns pages with postcards done by the same company.

Now the translation of the dedication (too bad the handwriting is not legible, help anyone?):
Mr. Antonio Albert
Weidemann, Mainz, (unreadable street name)
In memory of/ honor of our ride on the tram line 4b from the main railway station to the steamboat quay.
Summer 1931
Now it makes you wonder who the recipient is and the story behind the train ride!

Here is the postcard:


Also I'm guessing that the bridge on the postcard is the Theodor Heuss Bridge (Mainz-Wiesbaden) since this is the only bridge over the Rhine river that was built pre-1931 (1885 to be exact). But I might be wrong.