  Let $X$ be a smooth proper curve defined over a field $k$. The
representability of the relative Picard functor is obstructed by a class
$\alpha\in\mathrm{Br}(\mathrm{Pic}_{X/k})$. We show the associated division
algebra on $\mathrm{Pic}^0_{X/k}$ has natural involutions. We show the class
$\alpha$ splits at some height one points in $\mathrm{Pic}_{X/k}$.
