It should be like this in the bottom of the cannister: 1 round rubber seal, about the size of a half-dollar outside diameter, maybe 3/8 inch wide, with a half-round profile. Sits in a groove in the bottom of the cannister. Metal inside this seal is part of the cannister, not a separate piece. This seal normally doesn't require replacement, and is not in the filter kit. Use a sharp, stiff pin to dig it out if you have a replacement, otherwise leave it there.
Inside the bore of the bolt hole in the bottom of the cannister, there is an o-ring. Also typically doesn't have to be replaced at each filter change. A long, sharp pin should help you dig it out if you have a replacement; not included in the kit. It's in a groove that runs around the outside of the bore.
Inside the filter head (the part bolted to the block) there is a very critical seal. It goes around the boss in the middle, is about 1/2 inch wide, and looks like a piece of black garden hose. This normally doesn't have to be replaced and is not in the kit, but you want to be very sure it's there because the oil won't get filtered if it's not. It might be stuck in place, don't disturb it unless you have a replacement.
Hope this helps!
George Davis
'69 280 SL Euro manual