Might be some traps there; there were a few companies that sold stationary engines with 'Simplex' in the name. 'Baltic Simplex' is fairly common, sold by the Baltic Simplex Machinery Co. Many [maybe all] of their engines were rebrands from local manufacturers, e.g. Ronaldson Tippett and Rosebery/Buzacott.
Hardman & Hall became 'Gearco Engineering' at some point, and still manufacture and support the Simplex marine engine line. They are now located in Seven Hills, NSW.
See
HERE .
