\documentclass{ppex}
\nonstopmode
\usepackage [all,poly]{xy}
\pagestyle{empty}
\setlength\textwidth{135.0pt}
\begin{document}
\ResetPreambleCommands
\ReadyForTheFray
\usepackage [all,poly]{xy}
\newcounter{node}
%
\[
\renewcommand{\objectstyle}{\scriptstyle}
\newcommand{\Letter}%
    {{\setcounter{node}%
     {\xypolynode}\Alph{node}}}
%
\begin{xy} /r11mm/:
  (2,4.8), {\xypolygon6{~*{\xypolynode}}}
 ,(2,2.5), {*{0}*\cir<5pt>{}
               \xypolygon6{~*{\xybox{%
              *{\xypolynode}*\cir<2mm>{}}}}}
 ,(2,0)  ,  {\xypolygon6{%
                ~><{@/_.5ex/}
                ~>>{_{\delta^{\xypolynode}_{\xypolynum}}}
                ~<<{@{=}}
                ~<>{|\uparrow}
                ~*{\Letter}}}
\end{xy}
\]
\end{document}