 The HP-01 used 7 light-emitting diodes (LEDs)/digit in a 7 digit + decimal point arrangement for its digital display.Introduced in 1977 at the height of the LED watch craze, five models were available, two gold filled models and three stainless models.Prices were from $450 & $550 for the low end steel or gold to $850 (the equivalent of $2,500 to $3,300 in 2014 dollars).