Help identifying tweeters

May anybody help me identify this tweeter? It has a hexagon base, 4 1/4-inch outer diameter. Thanks.
Try at DIYaudio.

Also, if it's ferrofluid you may just need to clean it and replace.
Thanks to Wolf_teeth at DIYaudio forum for identifying this speaker as  a SEAS hexadym design.
That's right. Thanks, Eric. You made it happen.