I pulled my rifles out and got to looking at them in more detail. Sorry I'm not ripping them apart for detailed pics.
The basic difference between the two as far as the internals are concerned, are that the spring on the Tantal is actual part of the plate that slides into the receiver.
The EG has a seperate spring from the plate, and it also has a cross pin that helps retain the lever and spring within the plate.
Does that make sense?