  Thin galactic discs and nuclear stellar discs (NSDs) are fragile structures
that can be easily disturbed by merger events. By studying the age of the
stellar populations in present-day discs, we can learn about the assembly
history of galaxies and place constraints on their past merger events.
Following on the steps of our initial work, we explore the fragility of such
disc structures in intermediate-mass-ratio dry encounters using the previously
constructed $N$-body model of the Fornax galaxy NGC 1381 (FCC 170), which hosts
both a thin galactic disc and a NSD. We dismiss major and minor encounters, as
the former were previously shown to easily destroy thin-disc structures,
whereas the latter take several Hubble times to complete in the specific case
of FCC 170. The kinematics and structure of the thin galactic disc are
dramatically altered by the mergers, whereas the NSD shows a remarkable
resilience, exhibiting only a smooth increase of its size when compared to the
model evolved in isolation. Our results suggest that thin galactic discs are
better tracers for intermediate-mass-ratio mergers, while NSDs may be more
useful for major encounters. Based on our simulations and previous analysis of
the stellar populations, we concluded that FCC 170 has not experienced any
intermediate-mass-ratio dry encounters for at least $\sim$10 Gyr, as indicated
by the age of its thin-disc stellar populations.
