# Appendix




:::{.remark}
Following \cite{AEGS23}, a **Kulikov model** is a $K$-trivial semistable model $\cX \to (C, 0)$ of a degeneration of K3 surfaces over a pointed curve $C$. 
For each such degeneration, one can define the dual complex of the central fiber $\Gamma(\cX_0)$. For Type II degenerations of K3 surfaces, this yields an integral affine $S^2$ with singularities of total charge $24$, and for Type III the dual complex is an interval $\bD^1$.
The additional data of an integral affine polarization $R_{\IA} \subset \Gamma(\cX_0)$ describes the KSBA stable limit of a degeneration $(\cX^*, \varepsilon \cR^*)$.
For Enriques (and hence Coble) surfaces, we take the corresponding dlt models $\cZ \da \cX/\iota_{\En}$ and half-divisor models $(\cZ, \cR_{\cZ}) \da (\cX, \cR)/\iota_{\En}$ where $\cX \to (C, 0)$ and $(\cX, \cR)$ are Kulikov and divisor models of their K3 covers.


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:::{.remark}
The following is a representation of a Type II degeneration -- it is a chain of surfaces whose dual complex is an interval $\bD^1$, where the ends $V_1$ and $V_n$ are rational and the remaining $V_i$ are isomorphic to $E\times \PP^1$ for a fixed elliptic curve $E$.
The intersections $V_i \intersect V_{i+1}$ are double curves isomorphic to $E$.

\begin{figure}[H]
\centering
\includesvg[width=\textwidth]{inkscape/type-ii-kulikov-degeneration}
\caption{}
\label{fig:typeiikdg}
\end{figure}

A Type III degeneration can be represented by a triangulation of $S^2$ with singularities, depicted as follows:


\begin{figure}[H]
\centering
\includesvg[width=\textwidth]{inkscape/triangulated-sphere-fan.svg}
\caption{}
\label{fig:triangulated-sphere-fan}
\end{figure}

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:::{.remark}
The following is a combinatorial representation of a Kulikov model for Sterk 2.

\begin{figure}[H]
\centering
\includesvg[width=\textwidth]{inkscape/ias-sterk2-kulikov-model.svg}
\caption{}
\label{fig:ias-sterk2-kulikov-model}
\end{figure}

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