In MMD 050725 Björn Isebaert asked about old cardboard music
books.  From the pictures posted under
http://users.skynet.be/fa580362/oldbookslabels.htm 
it becomes definitely clear that these music books are for the
30-note Piano Melodico.  I have exactly the same music book labels:

 Nr. 347: O Tannenbaum
 Nr. 537: Marsch: Hipp, Hipp, Hurrah!
 Nr. 571: Marsch: Schwalben Marsch
 Nr. 646: Walzer: Wie suess

All these labels also show the titles in printed French and English
letters, Nrs 537, 571 and 646 also in Cyrillic letters.

The labels do not show a name of who punched the books; maybe somebody
could identify the maker by the graphics on the labels.

The measurements given by Björn fit the measures of the Piano Melodico
books but they have only 30 notes, not 32 or 33.

Regards from Germany
Christian Greinacher