this Arabic 3. All I can say is that the choice of a modern font for the Arabic numerals of the Vingt-8 and now the Tonneau, contrasting with the very traditional technique of guillochage and the observatory hands, seems deliberate to me. The goal seems to preserve the best of tradition while giving the watches a contemporary look (the bold colors of some dials go in the same direction imo).
Just my impression, for what it’s worth…