It looks like Crosby's early model, patented in the 1880's with some later improved models that you can't tell apart without inventoring the contents (an electric device was added at some point)
The Maritime administration department of the Dept Commerce wasn't formed until 1935 however, and probably wasn't doing anything usefull until 1939 or so......
The thing is for making steam indicator cards. The string goes to the steam engine crankshaft and moves the drum, creating the X axis on a graph card placed on the drum. The piston/spring thing has the pen, and measures the steam pressure in the cylinder making the Y axis on the card. The result is a graph with a trapizoid like drawing on it that tells you everything you could possibly want to know about your steam engine, like efficiency, generated power, valve leakage, headspace.....
The maritime administration was primarily responsible for the Merchant Marine, and equipment on the ships would have been privately owned, so I suspect it is from the standards department, for approving and certifying engines for new ship designs...(only a guess)
