This Heuer Chronosplit ref. 100.703 produced around 1975-1976.
It is very difficult to find in good condition and fully functional. Here is a unique opportunity to see the disassembled module of this model (see pictures).
What I have to mention is that this first version (LCD / LED ref. 100.703 ) is better done because the microprocessors on all three separate modules in watch are protected while on the (LCD / LCD ref. 102.703) version the micro connections on the processors are unprotected and this is the most common cause of failures of these watches.
The Heuer chronosplit version with LCD / LED display is an early version and was produced very briefly from 1975 to 1976 when it was replaced by the full LCD version which made until 1982.
When I first saw this watch, I didn’t understand why they combined LED and LCD technology?
If there was already exist LCD display at the time, why did Heuer use an LED display on the stopwatch, which consumes much more battery power, and which is difficult to read in bright light and sun ?
When this watch was developed as a project in mid 70s, there was an LCdisplay, but those early LCD versions were quite slow in showing the digits, which is not a problem for a watch, but it is big problem for a stopwatch because it shows 1/10 sec. which must be displayed quickly and accurately, the LED display could do that. That is the reason why the display on the stopwatch is LED. As 1976, more technologically advanced versions of the LCD replaced the LED display and the Heuer chrono split became a full LCD.
For me, this first version is one of the holy grails, and even today it looks futuristic when the world is full of all kinds of technological achievements. Imagine what 1975 this watch looked like on the wrist, pure science fiction …