  We study an interstellar signaling scheme which was originally proposed by
Seto (2019) and efficiently links intentional transmitters to ETI searchers
through a conspicuous astronomical burst, without prior communication. Based on
the geometrical and game theoretic viewpoints, the scheme can be refined so
that intentional signals can be sent and received after observing a reference
burst, in contrast to the original proposal (before observing a burst). Given
this inverted temporal structure, Galactic supernovae recorded in the past 2000
years can be regarded as interesting guideposts for an ETI search. While the
best use period of SN 393 has presumably passed $\sim$100 years ago, some of
the historical supernovae might allow us to compactify the ETI survey regions
down to less than one present of $4\pi$, around two rings in the sky.
