(I can remember the simpler functions (multiply, divide & the
  like) but how to use the thing for calculus &
whatnot I'm sure has
 "slipped" my mind... (lame) Pun intended ;^> 
Lame is right --
you're slipping.
You can'y use 'am for calculus...you must be thinking of trig.
 And tho we did have some TRS-80 Model 4's (and an old IBM Series/1) in 
high
  school, I did use it occasionally during geometry /
algebra class when
 necessary -- took it to college a few times to, but just to watch people
 gawk... ;-) 
I went through Navy Nuclear Power School in '76, and they were
required...even tho' calculators were cheap, then.
Texas Instruments was naming some of their calculators "SR" (for Slide
Rule) up until the mid-80's, at least. My first one was the SR-10...the LED
"wedge". $110, IIRC
Was that TI's first?
manney