Hi Lia,
I noticed in your other thread with the mexican fakes that you wondered wheather other characthers or only the smurfs was released with this marking. The Snorks are marked with SEPP also. So I found this information for you:
"The creation of the Snorks took place in Belgium, created by Nicolas Broca in 1982. SEPP, the animation department at Dupuis, handled the delicate and sometimes difficult licensing of The Smurfs products. SEPP wanted another big success like the Smurfs and so Les Snorky - the Snorks, were born. The Snorks didn't become well known until Hanna Barbera animation created the Snorks TV Show, which ran for four years, from 1984 to 1988. Snork figurines, books and other collectibles followed after the debut of the cartoon, and the Snorks slowly but surely developed a fan base. The Snorks may not have been on TV as long as the Smurfs, but they are just as fun!"
So the S.E.P.P. was handling the licensing of the smurf products.
And I have a few different items with this marking also like the "handcraft" pictures with smurfs I showed long time ago.