I have a 35 year+ in-ground gunite (?) pool that I've been told is a Sylvan pool. I'd like to replace the current incandensent 500 watt bulb with PL-5819. My problem is that there is absolutely no markings on the lamp housing or any where else on the unit. The lamp housing has never been touched or replaced although the pool has been renovated twice since we have lived here for over 29 years. The lamp housing has the electric cord entering somewhat below the center point of the back of the housing,
Fro the limited info above, can someone help me determine if the PL-5819 will fit the housing?