Eulenburg.
The pocket study score, since 1874. Founded in Berlin by Ernst Eulenburg, the imprint pioneered the pocket study score as a category — small format, scholarly editorial, the working analysis tool of the conservatory student. Now part of Schott Music with over 1,500 numbered scores.
Eulenburg's pocket study score was the first portable scholarly edition — affordable, durable, with critical apparatus, and small enough to carry to lectures, rehearsals and concerts. Every conservatory student of the past century has owned a stack. The numbered Eulenburg series, from No. 1 (Beethoven's Symphony No. 9) onward, is itself a canon.
Below: the Eulenburg departmental catalogue. The numbered scores are organised by composer for the major heritage works (Bach through Mahler). Plus the Eulenburg orchestral scores with audio CD editions and the modern critical scores (Eulenburg Audio+Score series).