Found out some new composer ID letters through the BMI repertoire. All of them involving William Loose.
AM - William Loose & Emil Cadkin (Later used by Erik Markman)
JB - William Loose (To 299, 560 & after), William Loose & Jack Cookerly (300 to 559)
MR - William Loose, Jack Cookerly & Emil Cadkin
OK - William Loose, Jack Cookerly & Emil Cadkin
