There are at least two variations of 515E.

This type(some of us call them "flat magnet" style) pretty much sucks, in my next life i will try them loaded with 416 parts:

515Ea.jpg

This type(rounded magnet) ain't so bad, IMO as good as 515G in the small horns like 828, 816, and 817:

ALTEC515E1.jpg

I tell a similar tale about the 416C...........................