The 5 minute flag requires some explanation. When the minute hand is positioned on the 11 the red flag will point at the 5 minute mark. In 4 minutes the red flag will move upwards and be positioned where the red 1 is. From that point on the flag will lower towards the red 0 and then it will drop signaling the end of the game.
It would be difficult to calibrate a clock like this lining up the minute hand on each side to look the same. The flag is a more accurate way to accomplish this and is done as follows : Advance the minute hand past the 5 minute mark on the dial (preferably closer to the 15 second mark). Setup a stop watch and start the chess clock. When the flag falls start the stop watch. Stop the stop watch when the flag falls again in 1 hour. There is an adjustment on the back of the clock for advancing or retarding the speed of the mechanism. Repeat this process until the clock drops the flag within 1 or 2 seconds of being exact. Several different trials will probably produce slightly different results. Just take the average and then do the same process for the other clock. At this point each clock should be with 1 or 2 seconds of each other and with the actual stop watch time for 60 minutes.
This clock has been calibrated and each clock side on average is the same and within 2 seconds of the 60 minute mark. This is not the most precise time piece. As a result wind-up analogue clocks have fallen out of grace with the chess world. Most use battery operated digtal clocks. The only problem is that the displays tend to be smaller and harder to read.
Each clock has a single main spring and a spiral spring mounted on the balance wheel. Great care has to be taken when disassembling this clock since the metal stops can bump into the delicate spring and if it does will probably ruin the spring and the clock is useless at that point.
After cleaning the internals each pivot was properly lubricated. They are tiny and a drop of oil is too much.
Each clock is mounted on what appears to be a vinyl backing. The buttons are heavy and feel like metal but can't be sure. There is one plastic gear within the workings of each clock.
Lifting the button assembly off the board is difficult because the metal band that stops the balance wheel when a button is pressed is very close to the balance wheel spiral spring. It would be quite easy to damage it.
The back is made from a brown wood grain plastic. Each adjustment for clock rate requires a small flat blade screw driver or the like.
Insa still makes this model of chess clock today and labels it "Made in Serbia". The newer clocks have a black back and the overall dimensions are smaller.
Taking these 2 screws out will allow the clock to be disassembled.
Insa Chess Clock (circa 1994)
Dimensions : 8.37" (length) x 4.37" (height) x 3.0" (depth).
A collection of images from a serviced and calibrated analogue chess clock from Yugoslavia. Manufactured by INSA (=INdustrija SAtova, Belgrad).
Housed in a beech wood case and glass protecting the face, its extra large size makes for easy viewing during play. The large buttons on top are easy to find and are quieter than brass buttons on similar clocks. Insa's unique five minute flag has 15 second increments in the final minute for blitz games. Also shows seconds ticking and can be heard 15 feet away in a quiet room. Not exactly a quiet clock. Will run 24 hours on a single winding.
Can't be sure when exactly this was manufactured but place it within a couple of years of the dissolution of Yugoslavia in 1992. Since that time former Yugoslavia has been divided into seven new countries. These countries, and their year of establishment are: Croatia (1991), Slovenia (1991), Macedonia (1991), Bosnia and Herzegovina (1992), Montenegro (2006), Serbia (2006), and Kosovo (2008).
The flash from the camera makes the piece look dustier than it normally would look to the human eye. You can zoom in on the images if you mouse over them. During autoplay zoom is disabled. Shrinking the browser window will shrink its contents possibly making it easier to view the gallery.
Valued in the range of $75 - $100.