The Square magnet woofer indicates they are the older version, which is a bonus in my view.
The tweeters are Foster, and can be swapped with the one commonly seen in Zenith Allegro speakers.
The E50's were my favorite of the range, with the bigger E90's a close second.
As an aside, in the model number, the "E" stood for "Efficiency" and the trailing two digits were the nominal cabinet volume in liters. The E90, however, actually had a 110-liter cabinet on the consumer version, and 120-liters in the pro version.
For a British speaker, they really were rather iconoclastic. Not in any way associated with the polite monitors and mini-monitors of IMF, KEF, or B&W. These were somewhat raw and in-your-face, and clearly designed for an American audience, or to steal sales from the likes of JBL domestically.