From SGS website...

SGS is a coin grading
company with the
highest standards of
quality and integrity.
We handle coins with
the utmost care and
attention. Each coin
is preserved in our
special holders,
serial-numbered and
sealed with our official
SGS gold seals.

From the Abon.com website...

Each coin comes slabbed in the protective SGS cases, sealed with the
gold SGS seals, and serial numbered. Your set also comes with a Certificate
of Authenticity from SGS with the matching serial numbers of your coins,
guaranteeing quality and genuiness.

My guess is that the "gold seals" are a special foil adhesive and the case is not ultrasonically sealed and easily opened.

Looking at this picture of some of them, they definately look like stickers.