[ARSCLIST] Columbia 7" 33-1/3 discs

[Steven Smolian <smolians@xxxxxxxxx>]

I have some Columbia 7" 33 1/3 rpm discs in test pressings.  They are on 10 7/8" plastic discs.  
There is a cut groove from 1.5 to 1.7.5 inches in from the edge in which the matrix number is inscribes.  The one I'm looking at is ZLP 1427.  This is followed by about a half inch of lead-in groove, then the recorded signal, another 1/2", then the end area, another 1-1/2", then the normal size 78 white label.  This one is Buddy Clark.  I have some with Doris Day as well, and probably others.

Any idea why these were pressed up in this way?  Were the commercial issues also pressed in a 10" press and trimmed?

Steve Smolian