Length of watch that I built was 14 1/2 inches long.
Length from top to pivot hole I set at one inch.
Viking navy watch
The only thing hard about making this watch is adjusting it to exactly one second. I ended up writing a computer program to help me time the period of the watch. Then I drilled a small hole in the bottom and screwed in a small long screw so I could make very small adjustments.
Once your watch is made, you need to dream up a way to attach it to your belt. I made a sash for mine. Works well and looks fine.
Note that in my left hand I have three strings of beads. One to count seconds. One to count minutes. One to count hours.
Viking navy watch with counting beads