I should also note that this was done by Lawrence Christian "Chris" Bohman for client Rosan Engineering.
Chris was the son of Christian Bohman, one half of the firm Bohman & Schwartz. The partnership of Christian Bohman and Maurice Schwartz ended in 1947. Christian Bohman named his new firm C. Bohman & Son. When Christian died in February of 1950, his son Chris took over the firm but retained the name C. Bohman & Son.