My ancient HP-28s is still working fine (it is my favorite calculator of all time), optimizing functionality and ease of use, but I fear its days are numbered. The battery port lid is cracked and spring loaded, and I fear it will not survive the next battery replacement. A piece of duct tape will not do, The port lid is an oddly shaped piece of plastic and it contains some conducting buses as well, so I can't replace it or jury-rig a kluge and I don't have the mechanical skills to make a new one. If anyone knows where I can find a replacement battery port lid I would be most grateful!

The HP28 series was the logical precursor to the HP 48s, which are highly backwards-compatible, so all the software I've written for the former runs great on the latter. Reverse Polish LISP rules!

Having researched this quite a bit over the last few weeks, I am finding myself in awe of the quality and innovation of the hp company, and the clever and dedicated engineers who worked there. But that was then, this is now. The business majors run the world now.