I agree, Jack Flower was likely the supplier or a locksmith who just made a key.
P. & F. Corbin was named for the two brothers who started the company, Philip and Frank. The company was later purchased to become part of the American Hardware Co. along with a division known as Corbin Cabinet Lock and the Russwin division, (originally Russel & Erwin). After a few owner changes CCL was sold off. Emhart Corp tried to change the name of the two remaining divisions, (Corbin and Russwin) unsuccessfully and eventually both of them were sold to Yale who in turn is owned by ASSA Abloy. A long history that started in the 1800’s.
BBE.