Texas Instruments Galaxy 67 calculator

Powerful programmable machine, but suffers from a couple of weak engineering technologies.
The case has a weak front panel made of easy breakable plastic in contrast with the back panel and hard cover that are made of good durable plastic.
The front panel suffers from premature wear as the painted surface is easily pealed off by the sliding hard cover.
Internally the LCD display uses a flat cable that breaks easily as well, even without manipulation, leaving the display with missing dots.
Features wise, the calculator is very good for its class.

The following item was made in 1993.

Integral of sin(x) from 0 to pi using 10 intervals:

 Sin( pi) according to this Texas 67 model. This deviates from what Texas does with all of their other models, where the result is exactly Zero.

 

   

HP-11C RPN calculator

This LSI technology used in these machine series is amazing.
After removing the batteries and let the machine alone for three days, I inserted the batteries to run the diagnostics once again to take these pictures.
After powering ON the calculator, I was presented with the exact contents I had three days ago in the stack.
This means an excellent battery backup capacitor quality able to retain its charge for several days in a row,  and extremely low leakage static memory - probably the best ever made!

National Semiconductor Novus 4510 Mathematician 1976

Classic RPN entry machine.