http://en.wikipedia.org/wiki/Casio
http://ja.wikipedia.org/wiki/%E3%82%AB%E3%82%B7%E3%82%AA%E8%A8%88%E7%AE%97%E6%A9%9F
The very first CASIOTRON is 02 series. 02 stands for the second module that is developed by CASIO but the reason why 02 is the first model instead of 01 is not explained in any of the materials. The very special feature of the first CASIOTRON is in the LCD display, there is no "Liquid Crystal" printing. Here are the models from early posters. The triangular engraving on the case back resembles the CASIO headquarter - Sumitomo building in Shinjuku in 70's.
Some appeared in Yahoo Japan auction and eBay from the past few years. These are the very rare pieces that are still running these days.
I am very lucky to acquire three pieces from the auctions.
In the later version, the Liquid Crystal is printed on the LCD.
