So I found an older 400w HPS lamp last night. I think it is an older Sylvania but am not sure. It has the same base and glass as a Sylvania but it has the same dimple on top as a GE or Philips. The etch is worn off and there are no other markings on it. Did Sylvania use the dimple design on their 250 & 400w HPS lamps at one time, and if so when did they use that design. The PC that was in the fixture was from 88.