Linear Low Pressure Sodium Lamp

This image is of 2 early linear 200W sodium lamps, both are marked as ‘Mazda Linear sodium made in Britain’. There is no SLI/H marking on the description. The lower lamp is of the Thorn design but I think it may have the earlier tin oxide coating inside. The upper lamp initially looks like the GEC design but it is different in many ways. There are 2 fewer crescents pressed into the discharge tube compared to the GEC and this lamp has metal supports rather than the mica used by GEC. There is no reflective coating in this lamp either but there is a secondary glass sleeve, as common in the SOI/H design. Just visible at the top is a painted conductive earth strip to aid lamp starting, as without the metalized outer coating, this is required for reliable starting. I also suspect the number seen stamped on the discharge tube is the date, as I suspect the lamp is from around 1969. I obtained 3 of these lamps from the one building when being decommissioned from their floodlights in the 1980s. The building was owned by the electrical contractors Balfour-Kilpatrick (Beatty), Paisley. The third lamp was identical to the top one and I swapped it with James some time ago. The upper lamp is showing signs of getter depletion. I would normally be tempted to re-fire the getters but there is a risk to the lamp and the vacuum is still present.