An Addiator? I haven't seen one of those since junior high. I had one, they were neat.
I had an HP-25C (IIRC) when I worked for the Navy in the late 1970s. Government property, so I had to leave it behind when I left in late 1979. Bought an HP-34C after I went to work for Martin Marietta Denver Aerospace. Great programmable calculator, but it didn't have enough memory, so I got an HP-41CV to replace it. I still use that one today, about 37 years later. I haven't written a program for it in decades, but I still use at least one today, calculates monthly payments for a loan. Feed it the amount borrowed, the interest rate and the number of payments and it spits out the payment. Works great. Every 10 years or so I have to buy a new set of N cells. Now that Radio Shack is gone I'm not sure where I'm going to find those. On-line, probably.
I'll bet I've got something older in my office. An Empire Devices NF-105. If you know what that is, you're an old fart like me. If not, ask and I'll tell you. Suffice to say that when I bought it my wife asked why and I told her it was because I wanted it. Paid almost as much to have it shipped up from San Diego as I paid for it.