A friend of mine sent this link to me as he knows that I've been an avid ECM collector for quite a few years.  I endeavored to collect on vinyl the label's entire output until ECM went to CD-only.  I've been adding some ECMs to my collection recently and I've just entered in my database Krakatu -- Volition ECM 1466.  This is the highest # I've seen on vinyl. 
 
As for the never-released-on-cd-ECMs: I'm not sure about the following -- someone please correct me if I'm wrong: 
 
1141 George Adams - Sound Suggestions 
1164 Abercrombie Quartet 
1191 Abercrombie Quartet   M 
1187 Rainer Bruninghaus   Freigeweht 
1901 Larry Karush/ Glen Moore   May 24, 1976 
1357 Hans Koch/ Martin Schutz/Marco Kappeli    Acceleration	 
1081 Art Lande  Rubisa Patrol 
1106 Art Lande  Rubisa Patrol  Desert Marauders 
1214 James Newton   Axum 
1071 Tomasz Stanko   Balladyna 
1160 Steve Swallow   Home 
1113 Tom van der Geld and Children at Play   Patience 
1224 Enrico Rava   Opening Night 
19003 Percussion Profiles 
19004 Manfred Schoof Quintet - Scales 
ECM/SP 2305 801 Peter Ruhmkorf - Kein Apolloprogramm fur lyrik