What is another word for a library stamp?

There isn't really a single perfect synonym for "library stamp" because it refers to a specific type of stamp with a specific purpose. However, here are some words or phrases that capture different aspects of the concept:

Emphasizing the marking function:

* Library mark

* Ownership stamp

* Circulation stamp

* Accession stamp

* Bookplate (though this is usually a sticker)

Emphasizing the design:

* Library logo

* Library emblem

* Library insignia

Emphasizing the function:

* Library identification

* Library registration mark

Ultimately, the best alternative depends on the specific context you're using it in.