(Cubic) stones come in many shapes and forms within Freemasonry. This specific stone (an oblong stone with a square laying on it) can be seen on the Second Degree “Orient Board” of the French Rectified Scottish Rite. The text “dirigit obliqua” translates to: “directs obliquely”. The same image was used in the Strict Observance.
original design from the Strikte Observanz (1742-1782), nowadays a common design in the French Rectified Scottish Rite. I found this modern image on nos-colonnes.com