1985 Minardi decal

I've finished seven teams for a 1985 race-by-race carset. The latest is Minardi, and I had pretty good luck, after spending hours searching online, in figuring out all the sponsors but one, circled in the attached picture. Minardi parted company with Ceramiche Montreal before the German Grand Prix; about the time of the Italian Grand Prix this white decal showed up under "Champion" on the side of the cockpit. This picture, from Wookey's collection, is from South Africa. Any help will be much appreciated.

i'm sorry for the late answer, but i'm sure the missing logo is Sintoflon. I have attached another phote, where you can see it a little bit clearer

I just now needed this in reworking 1985--thanks very much!