SELZ DRV 750 Soviet self ballasted mercury vapour lamp for greenhouses -- after glow

mercury vapour lamps become fairly popular for the use in Greenhouses after they were launched and before HPS become popular, as well as in small domestic applications were growing HPS lamps were never made in small enough wattages. One example for the latter is the Osram HQL-R Delux 80W which can also be seen in this album.
For industrial settings the 400W Lamp become popular. It was sealed in the slightly bigger 700W envelope to allow a better beam positioning and uniformity. These lamps would be mirrored or have a titan oxide reflector, which allowed cheap fittings and a new reflector with every lamp. The eliptic shape allowed a more compact lamp setup. The first lamp of that type that was commercially launched is the Philips HLRG which can also bee seen in this album.

The soviet for them self did also copping this design of lamp with the ????400-1 lamp. eventually this lamp was also improved with an extra layer of phosphor. These lamps were vital because of the short growing seasons in some parts of the soviet union.

However the soviet scarcity economy-fueled by communism- lead to problems providing ballast so this self ballasted lamp was developed.