The key to this is finding other test pressings with the B/S rubber stamp.
From: Association for Recorded Sound Discussion List
[mailto:[log in to unmask]] On Behalf Of Jay Bruder
Sent: Sunday, October 29, 2017 10:04 AM
To: [log in to unmask]
Subject: [ARSCLIST] original recording to test pressing timeline in 1949 ?
Does anyone know how long it took to turn an original recording into a test
pressing in the late 1940s? How long did each plating stage take? We are
trying to assess the validity of a recording session date reported to have
been held in Columbus on Thursday January 27, 1949 and a test pressing
-presumably for Savoy in Newark- inspected the next Tuesday, February 1,