The following information was provided by Phillippe Caulliez
The Sharp EL-5101 was the first from a long range sold from 1981 (1979 in Japan) to 1985.
They are in order : 5101, 5100, 5102 (a 5101 financial) and 5103.
Then, Sharp introduced a second generation where the LCD changed from from yellow to grey
and the calculators had more functions : 5100S, 5103S, 5050 and the best - the ultimate 5150.
This set of images © Barry Smith, 2005