According to a quick Google search I did just now “Signal Engineering & Manufacturing Company” later became “Wheelock Signals, Inc.”. Here’s also a 1938 Wheelock/Signal Engineering catalog that I found, which features the very same pull station you have on pages 6 & 8 (which gives an idea of its age):
Wheelock apparatus. : Signal Engineering And Mfg. Co. : Free Download, Borrow, and Streaming : Internet Archive