Mozilla 1.77 S/MIME toolbar button missing

I'm running Mozilla 1.7.7 & SuSE Linux 9.3, on two different systems.  On
the notebook computer, when composing a message, there's a button for
S/MIME.  However, on my desktop system, that button doesn't appear, and I
have to select "Options > Security", to see the S/MIME options.  Is there
any way to enable the S/MIME button on my desktop system?

tnx jk