  Luminous Blue Variables (LBVs) are massive stars that show strong spectral
and photometric variability. The question of what evolutionary stages they
represent and what exactly drives their instability is still open, and thus is
it important to understand whether LBVs without significant ongoing activity
exist, and for how long such dormant LBVs may ``sleep''. In this article we
investigate the long-term variability properties of the LBV candidate MN112, by
combining its optical and infrared spectral data covering 12 years with
photometric data covering nearly a century acquired by both modern time-domain
sky surveys and historical photographic plates. We analyze the spectra, derive
physical properties of the star by modelling its atmosphere and use a new
distance estimate from Gaia data release 3 (DR3) to determine the position of
MN112 both inside the Galaxy and in the Hertzsprung--Russell diagram. Distance
estimation increased in almost two times in comparison with Gaia DR2. Due to
that MN112 moved in upper part of the diagram and according to our modeling it
lies on evolutionary track for star with initial mass $M_*=70 M_\odot$ near
Humphreys--Davidson limit. Given the absence of any significant variability we
conclude that the star is a dormant LBV that has been inactive for at least a
century now.
