hey shorebird, not totally sure but i purchased the standard 525, added the tourn handle and a knobby side plate for more magnetic control. seems to be the same now. i also would like to know if there are any other diferences, neil mackallow who helped design the reel could probably tell us more. he is the one who sold me my side plate when i couldn't find one anywhere else. need his web site let me know, he does check it and has a message board.