Actually the late G rolls by Automatic are 4X rolls.  Starting
somewhere in the 600 series you will find 4X arrangements intermixed
with G (pipe arrangements).  It seems likely that when the large
Seeburg G started to decline in sales and the KT model started to sell
well that Seeburg (Automatic Music) started changing the rolls to 4X
type arrangements.  This was in the early 1920's.

Don Teach