Dan Henry 1939 Military Chronograph instructions

The Dan Henry 1939 military chronograph is all about function. I pay tribute to these sophisticated timepieces worn by military officers who used the scales to calculate distance, speed, or even heart rate. They were the smartwatches of their era.
Your Dan Henry 1939 Pilot Chronograph is equipped with the Miyota caliber 6S21 60-minute chronograph with smooth motion center seconds.
The left subdial shows the chrono minutes; the right subdial shows the running seconds of the watch.

1. Setting the time

• Pull out the crown.
• Turn the crown to set the hour and minute hand.
• Push in the crown to the normal position.

2. Using the chronograph

Your Dan Henry 1939 Military Chronograph features a stopwatch that can measure up to 60 minutes.

• To start the chronograph: press the upper pusher. The chronograph hands will move.
• To stop the chronograph: press the upper pusher again. The chronograph hands will stop and show the elapsed time. (Read the elapsed seconds on the large central hand and the minutes on the sub-dial in the 9 o'clock position).
• To reset the chronograph: press the lower pusher to reset the chronograph. All the chronograph hands will be reset to zero position.

Note: The Dan Henry is a 60-minute Chronograph, so the chrono will stop running after 60 minutes.

3. Aligning the Chronograph hand

If the central seconds hand does not return to zero, you can reset the hand like this:

• Pull out the crown.
• Press the upper pusher once to set the chronograph second hand to the zero position.
• The chronograph hand can be advanced rapidly by continuously pressing the pusher.
• Once the hand is set at zero position, reset the time and return the crown to its normal position.

4. Setting the date (for watches with date windows)

• Pull out the crown to the first click position.
• Turn the crown clockwise to set the date.

Note: Do not change the date when the hands are set between 9 PM and 3 AM, because the day may not change properly. To set the date during that time, first change the hands to a time outside of that range; set the date, and then reset the correct time.

5. Measurement scales

The Telemeter scale determines the distance from the wearer to an event that can be both seen and heard.
For example, is a lightning storm moving closer? Start the chronograph timer when you see the flash, stop it when you hear the thunder clap. Reading the distance in miles or kilometers on the telemeter scale.

The Pulsometer is a specially calibrated scale used to determine heart rate.
Start the chronograph timer and count 15 heart beats. Stop the timer and read the heart rate in beats per minute.

The Tachymeter scale can be used to compute a speed based on travel time. The tachymeter can also be used or measure distance based on speed.
To measure speed: To use the tachymeter for measuring speed: start the chronograph at the beginning of a 1-kilometer or 1-mile distance. At the end of the distance, the second-hand points to indicate your speed.
To measure distance: while traveling at a constant speed, the tachymeter can be used to measure distance. Start the chronograph at the beginning of the length to be measured. When the second-hand reaches the point on the tachymeter scale where the speed indicated equals the speed of the vehicle, one unit of distance has been covered (miles if speed is miles per hour, kilometers if kilometers per hour, etc).
For example, if you travel at a constant 80 mph (or at 80 km/h), then the distance traveled while the second-hand sweeps to "80" (45 seconds) will be exactly 1 mile at 80 mph (or 1 kilometer at 80 km/h).

6. Water resistance

Your chronograph has been tested for water resistance. It is safe to wear in a swimming pool, but not for scuba or ocean diving. The crown must be pushed in to ensure that the watch is water resistant.

7. Accuracy and battery replacement

Your Military Chronograph is accurate to 20 seconds a month.
With normal use, the battery should last about three years.   When the watch begins to run slow, the battery should be changed. Use a ref. SR927W or 395 battery.  
The battery can be conserved by pulling out the stem and stopping the watch.