OSRAM SO/H Lamps in Collection
140 W (equivalent of 90 W SOX)
This lamp's arc tube carries the characteristic brown tinge that these lamps acquired after many hours' use.
Removing the delicate arc tube from the outer jacket also reveals heavy blackening to the electrodes.
The OSRAM frank for the outer jacket is stamped on the inside of the glass, so as to avoid its accidental removal during cleaning. The date code (QH) suggests that the glassware dates from August 1959.
By contrast, the GEC stamp on the porcelain rear section of the arc tube is barely visible. There is damage to the other side of the arc tube (probably caused by the stresses placed on the glass by the electrodes), which has caused the metallic sodium within the arc tube to oxidise; eventually becoming sodium oxide.
The insertion point of the arc tube is designed to minimise heat losses.
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