I credit the HP-41CV I had in in high school for growing my interest in programming. Through college it was an HP-48G. My father-in-law recognized my love for these devices later by giving me his old HP-35, complete with manuals and a couple accessories.

One of the more interesting accessories was his special HP-35 hardcore looking security lock. You would securely bolt the base of the lock to your desk, place the HP-35 inside, and connect and lock the cover with a key. Precious device back then!