D. Gruen & Son was founded in 1894 by Dietrich Gruen and his son, Fred, after the previous company he founded, Columbus Watch Manufacturing Company in Columbus, Ohio, went bankrupt. Dietrich is known for a patent he took out for a safety pinion (U.S. patent no 157'913) for pocket watches. The pinion prevented damage to the movement if the mainspring broke.
When Dietrich's other son, George, joined the company, it was renamed D. Gruen Sons & Company. Gruen focused his business on importing movements from Switzerland and casing them up to be sold. In 1904 Gruen rearranged pieces of the pocket watch movement to make it a third thinner than most others and still meet railroad requirements.
In 1924 in honor of the 50th Anniversary of Gruen's patent for an improved movement piece, the company released a pocket watch with a movement made of pure gold. 600 of these pieces were produced-one for each month of the 50 years. The quality of these pocket watches was impressive, elevating Gruen's reputation.