Okay, I think we have this entire mystery figured out.
?We know that the siren is a Hormann ECN
?When I went to Millington, I saw a Thunderbolt on the NAS. It wasn't labeled on the map of sirens because I had placed the marker about 800 yards west of the siren, thinking that a utility pole was a siren (from the looks of it on Google).
?The 'old, white siren' turned out to be the Thunderbolt, which is 112 yards away from the Hormann.
Thanks guys for all of your help! I'll try to get some of my own pictures later.