--list-keys lists items that I cannot find in Keychain Access

Hi everyone, allow me to ask for some help here.
I use Nexus' "Personal Desktop Client" as a middleware, it recognizes my smart card nicely if I put it in the reader.
Also, when `smimesign --list-keys`, the items I expect from the card are listed.
However, I cannot find them reflected in Keychain Access. Where are they (from)?
Background is: I want to make use of Acrobat's PDF signing but that does not work this way, it doesn't discover the identities…

Any help is much appreciated!