Hi
The rebated base is a narrowing of the bullet normally a revolver bullet with a flat base or with a small hole. I have included 5 revolver bullets showing a rebated base, a glued paper base, a tie ring or ring tail, a paper bullet with tie ring and a serrated bullet which had either a paper or linen covering the powder and was glued to the bullet. It might have been a collodian attachment also. I hope this helps out on the rebated base question.
Tom Stelma
Tom