  The gauge invariance of open string field theory is considered from the point
of view of level truncation, and applications to the tachyon condensation
problem are discussed. We show that the region of validity of Feynman-Siegel
gauge can be accurately determined using the level truncation method. We then
show that singularities previously found in the tachyon effective potential are
gauge artifacts arising from the boundary of the region of validity of
Feynman-Siegel gauge. The problem of finding the stable vacuum and tachyon
potential without fixing Feynman-Siegel gauge is addressed.
