H. Morin started a business @ rue Boursault nr. 3 around either 1860/1880 ('contrary/dueling' data on date of origin) in Paris , whose primary product line was a variety of mathematical instruments , including (but not limited to) survey instruments , tachymetrical slide-rules and map-making tools .
The U.S. Army Signal Corps used a couple of his instruments during the first World War , original one of which is in the image below .
The business moved from its' old address around the turn of the century to 11 rue Dulong , Paris .
Rumor has it that 'they' were still in business in France in 1954 .
There's a nice PDF at -
www.rechenschieber. org/stadia.pdf , with a couple of nice images of an H. Morin 19th century tachymetrical slide rule that had been constructed in 'German Sliver' .
I'd give my very best guess that your stopwatch item may be from the 1890's , and was intended for TSD calculations (time,speed,distance) & it's a bit of a pity that the back is missing .
Cool little item , EditedAbyss !