HP (HP-25C) RPN - C for continuous memory so you didn't lose your traverse distances & bearings traversing with a theodolite and chain, my favourite calculator whilst working as a land surveyor in the 1970's in BC, Canada A stack calculator no = used, 2+2 Enter 4, ditto for - x divide Cost me $275 The Bay in Vancouver in 1976. Too late for my response but got my story in! Intelligence
Ability (something our team certainly doesn't have right now - what a shambles as my Kilburn Dad would say!)