Joined: May 2008
Posts: 10,106
Likes: 2,756
From: Fredericksburg, Va
Bikes: ? Proteous, '65 Frejus TDF, '73 Bottecchia Giro d'Italia, '83 Colnago Superissimo, '84 Trek 610, '84 Trek 760, '88 Pinarello Veneto, '88 De Rosa Pro, '89 Pinarello Montello, 'Litespeed Catalyst'94 Burley Duet, 97 Specialized RockHopper, 2010 Langster
Based on picture number 4 you have 550. Look at the right exploded view, DS bearing and compare it to the right side exploded view, DS. The left view shows a "Cap" that covers the bearing on the 500. The right shows the bearing at the location of the "Cap", which is effectively further out from the center of the hub. This is the difference between the 500 and 550 RD's.
I envy your wheel set, BTW! Mine came well used and with SACH skewers ILO Mavic original ones. There were two levers materials, steel and aluminum. Which do you have?