1967

The picture shows the oldest light bulb in my collection. I bought it last year. It's purple. It gets very hot. The filament is made from carbon.

Tesla SHC400 high pressure sodium lamp of early design, possibly of 1967, developed by Otto Sofka and Milan Neužil. The arc tube has niobium caps on the end seals, same as with the GE American lamps of this time. Getters of the outer jacket are unusually parallel mounted.