Did you know that before publishing The Diamond Necklace in 1923, Gregg serialized the identical shorthand plates in four 1921 issues of the Gregg Writer?
The installments were in the following issues:
Gregg included the last page in September 1921, which started a new volume and a new yearly subscription. This would mean that readers would have to renew the yearly subscription (September through August) to get the last installment. (Starting in 1924, the Gregg Writer published only Sept through June.)
I have the 1923 publication, and the plates are identical to this 1921 serialization. Attached is a scan of the Gregg Writer covers and installments of The Diamond Necklace from 1921. The plates were created by Georgie Gregg Gingell, who also did the plates for Alice in Wonderland.