While looking at Osram’s 400w metal halide lamps for the European market, I have noticed that the HQI-E 400W/N/SI and the HQI-T 400W/N/SI lamps are designed for use on 400w mercury vapor ballasts in conjunction with a low voltage ignitor while I have seen that some of Osram’s HQI-T 400W/N; HQI-BT 400W/D; HQI-E 400W/N; HQI-E 400W/D metal halide lamps are designed for use only on 400w high pressure sodium ballasts while others are designed for use on both 400w high pressure sodium ballasts and 400w mercury vapor ballasts. I would like to know which of these lamps are designed for both mercury vapor and high pressure sodium ballasts and which ones are designed for high pressure sodium ballasts only.

There was a heated discussion here https://www.lighting-gallery.net/gallery/displayimage.php?album=7724&pos=1&pid=225308 some time ago on these lamps, generally the idea is that /D version historically was designed to run on mercury ballasts first, then upgraded to support both mercury and sodium, but today's datasheet support only running them on sodium at ~4A.