Lia found this information in one SCCI letter. Number 13.
There it says that you can see the schöllerpromo pictured on a W Berrie poster from 1980.
So with this information and also the picture of the icelollysmurf with the hole in the hand on the 1980 german poster, I am pretty sure the schöllerpromo was the first variation made of this smurf. Made in 1979 and then sold with the Schöllerflag.
And as Schleich did before they used this promo when taking the pictures for the 1980 poster, because that was the one they already had then. Just like with the National cleaner in the Schleich catalogue.