  While theoretical dust condensation models predict that most refractory
elements produced in core-collapse supernovae (SNe) efficiently condense into
dust, a large quantity of dust has so far only been observed in SN 1987A. We
present the analysis of Spitzer Space Telescope, Herschel Space Observatory,
Stratospheric Observatory for Infrared Astronomy (SOFIA), and AKARI
observations of the infrared (IR) shell surrounding the pulsar wind nebula in
the supernova remnant G54.1+0.3. We attribute a distinctive spectral feature at
21 $\mu$m to a magnesium silicate grain species that has been invoked in
modeling the ejecta-condensed dust in Cas A, which exhibits the same spectral
signature. If this species is responsible for producing the observed spectral
feature and accounts for a significant fraction of the observed IR continuum,
we find that it would be the dominant constituent of the dust in G54.1+0.3,
with possible secondary contributions from other compositions, such as carbon,
silicate, or alumina grains. The smallest mass of SN-formed dust required by
our models is 1.1 $\pm$ 0.8 $\rm M_{\odot}$. We discuss how these results may
be affected by varying dust grain properties and self-consistent grain heating
models. The spatial distribution of the dust mass and temperature in G54.1+0.3
confirms the scenario in which the SN-formed dust has not yet been processed by
the SN reverse shock and is being heated by stars belonging to a cluster in
which the SN progenitor exploded. The dust mass and composition suggest a
progenitor mass of 16$-$27 $\rm M_{\odot}$ and imply a high dust condensation
efficiency, similar to that found for Cas A and SN 1987A. The study provides
another example of significant dust formation in a Type IIP SN and sheds light
on the properties of pristine SN-condensed dust.
