In May of 2002, I made a tiny watch PC board using the above circuit. It was about 1.25" square. The tube leads were bent over and hand-wired into a zigzag hole pattern on the board. The battery I chose was a CR2 lithium camera battery, 1" long and 5/8" diameter. The time-setting buttons were replaced with magnetically activated reed switches to eliminate the need for pushbuttons poking out of the case.
I had put in a tilt sensor, the exotic ADXL202 part from Analog Devices, because I wanted the watch to display the time without having to push a button. I worked out an algorithm for detecting the tilt of the wearer’s arm, and watched myself at work and play to make sure that my arm didn’t reach that watch-reading tilt position inadvertently. I was satisfied that it would work. However, I had to mount the tilt chip at right angles to the PC board so it could monitor the proper two axes that indicate wrist tilt angle.
I made three of these boards. I wore one for over a year, tucked in a little Hammond plastic box glued to a Velcro watchband. I sold another to my brother, who put it in a very classy copper case he made from sheet stock. He still wears this watch. The third was eventually sold to a NeoNixie member. They all still work, I think. I had to replace a couple tubes due to elements shorting together. This was very tedious work, and indicated that tube sockets are needed for a real product.