Complex sentence: Effects of gravity on an escapement can have quite significant effects with slight variations of position, even if a pocketwatch was most of the time in a breast pocket, the exact position could still vary over 45 °.
Split into simpler sentences: Effects of gravity on an escapement can have quite significant effects with slight variations of position. Even if a pocket watch was most of the time in a breast pocket, the exact position could still vary over 45 °.