I have some Columbia transcriptions and sleeves that specify NAB.......   
Somewhere in the past  perhaps Oliver Reads Recording and Reproduction of Sound i believe mentions NAB and Columbia early lp's.
I know it says on some Cook LPs use NAB curve.  
As for Columbia studio equipment ive seen pics of Altec A7 voice of theatre  speakers...... these had a very hard  high end  and that could account for the lack of highs on some Columbia  discs  they  rolled them off cutting the master  because of the  high peak of the A7 they were hearing. 
d nelson ward  
 
 
Beautiful Music you will never forget, at; http://www.americanbeautiful.podbean.com/




________________________________
 From: Art Shifrin <[log in to unmask]>
To: [log in to unmask] 
Sent: Saturday, June 2, 2012 4:52 PM
Subject: [ARSCLIST] CBS / Columbia pre-mastering 78s & LPs on 33.33 standard groove lateral cut lacquers
 
Is it KNOWN via what playback equipment (turntables, preamps, arms,
pickups) they used to
master 78s & their early microgroove LPs?  If so, what were they?  And,
with what EQ were those submasters recorded?  NAB? Orthocoustic? Something
else?

Thanks,
Art (Shiffy) Shifrin