The HP 35 calculator was introduced in 1972. The early models aren't quite fifty years old yet, but will be later this year. Many (most?) of these still work just fine from the mains adaptor or once you replace the batteries.
It came out as new, the only issue is one of the display segmemts on fifth number (from left) not lighting up, luckily it is the right bottom one, so it is still "readable".
My HP 28-C (circa 1987) is still going strong, and it is 34 years old by now.