[78-L] Columbia R series

[Han Enderman]

What is the Columbia R series?
See for R-2324 by Laycock & Mather:
http://www.ebay.com/itm/Arthur-Laycock-George-Mather-Cornet-Duet-Ada-and-dot-Friendly-rivals-78-/261249869094?pt=Music_on_Vinyl&hash=item3cd3b4a526#ht_765wt_915

It appears I have 4 other label images from this rare series, 
with 3 different Columbia label types (also large magic notes and black).
These other issues are :
R-1946/47 Peter Wyper, 
R-2944 Temple Quartette
& R-69149 (with printing code TBW) Clara Butt (1-sided).
Other issues known?

han enderman