On a question by Firey concerning uniqueness

We prove that the curvature equation $\sum_{j=1}^n α_j E_j(τ_{\mathcal{M}})=\sum_{j=1}^n α_j E_j(τ_{\mathcal{N}})$ yields uniqueness up to translation for any two closed $C^2_+$ hypersurfaces $\mathcal{M}, \mathcal{N}\hookrightarrow\mathbb{R}^{n+1}$ whenever $(α_1,\ldots,α_n)\in\mathbb{R}_{\geq 0}^n