Product information "PREMIUM Window Pen"
Uses:
A covering lacquer pen for the colouring of mitre joints. Optimized tip and lacquer quality ensure a continuous lacquer flow. Recommended for indoor and outdoor use.

Characteristics:
Dries quickly, wipe-resistant, scratch-proof and overcoatable. Acrylic-based.
https://heinrichkoenig-shop.de/media/b4/f2/4a/1671546569/2435x6_fenster-fix-premium_gebr_2021-27_web.pdf
https://www.koenignorthamerica.com/media/4f/9d/77/1685430969/TDS_2435x6_PREMIUMWindowPen_2021-43.pdf