Billy Mood is a good start:

http://www.terebess.hu/english/yixing1a.html

Look for "The Seal Chops of Zisha Teapots".

In particular note this bit:

"During the Cultural Revolution period from 1966 to 1976, potters were
not allowed to imprint their personal seals on teapots. To resolve the
problem of identifying the works after firing in cases of breakage or
deformity, numbers were used to identify each potter."'

Please share any other information that you come across in your search.

Patrick