  Spectroscopic observations provide evidence that the optical transient object
observed in 1966 on archival plates of Sonneberg Observatory is a B=18.5 dMe
star. For an assumed flare duration of 40 min. (or longer) the flare amplitude
was $\bigtriangleup$m$_{B}$ $\approx$ 5.2 mag. If the recorded event was
belonging to the class of 'fast' flares its amplitude could have reached 7-9
mag.. We estimate a lower limit for the optical flare energy release of
10$^{35}$ (d/100 pc)$^2$ erg/s. We discuss the positional coincidence of this
large amplitude flaring star with the error box of the $\gamma$-ray burst 1978
October 6B and conclude that the flare star is probably not related to the
$\gamma$-ray burst. The fact that no other optical flare was found from this
object restricts their frequency to be less than 7$\times$10$^{-4}$ h$^{-1}$
for amplitudes (in B) greater than 4.5 mag. Nevertheless, large amplitude
flares constitute a serious background problem for the wide field search for
possible optical counterparts of $\gamma$-ray bursters.
