One of the Chronomaster's selling points at the time (around the 1960's) was the fact that its a Super Chronograph. Almost all Chronomaster models have a consistent feature which consist of your typical chronograph, water resistance for upto 200m, tachymeter scale, a rotating bezel for diving, a secondary time zone (on the bezel), and a regatta countdown timer (the red triangle marker) on the 3 o'clock sub dial. 
 
Nivada/Croton watches has an interesting history. The Movado watch company felt threathed by the fact that Nivada was planning on importing watches to the United States. Perhaps Movado didn't want their sales weaked by the newly imported watches. They prevented the name Nivada be used but allowed it to be combined Grenchen. Eventually, the Croton Watch company were able to import watches after it had been thrown out of the court in New York in 1939. The details of this litigation is located under the Second Circuit, Docket 22869 of the United States Court of Appeals.
 
This Chronomaster is in great shape despite its age. One of it's distinct feature is the 12 o'clock applied marker painted partialy red. The lume markers and lume on the minute and hour hands are all original tritium lume.