I love my 28S bought used 20 years ago for $100. When I got my first real engineering job, you could tell the age of the engineer by the era of HP calculator o

I love my 28S bought used 20 years ago for $100. When I got my first real engineering job, you could tell the age of the engineer by the era of HP calculator on their desk (or frequently in their hand). One guy had one with red 7 segment lights and 4 slots in the back, lots of guys had the engineering version of the 12, I had my 28S, and a couple young-uns had the 48. There was one guy with a TI, but he didn't last long. I find I'm a lot better with the 28 with it's 3 or 4 visible stack items than the single visible one of the smaller calculators. But it is a lot bulkier, and i teats batteries. I think I've had to replace them 5 or 6 times in the time I've owned the thing.