Identify part please!?!

Aloha, I have an opportunity to pick up a 7.25 sure grip third member. Only problem is...I wouldn't know a sure grip third from a fourth or fifth!

Can anyone clue me in on what to look for? What else I might need with it? I guess its smart to keep the pinion and ring together?

see picture for details....:-D

Mahalo Mike

sure grip 3.23 small.jpg