  We report a study of the organic compound $(TMTSF)_2 ClO_4$ in both a sample
cooled very slowly through the anion ordering temperature (relaxed state) and a
sample cooled more rapidly (intermediate state). For the relaxed state the
entire sample is observed to be superconducting below about T_c ~ 1.2 K. The
second moment of the internal field distribution was measured for the relaxed
state yielding an in-plane penetration depth of ~ 12000 Angstroms. The
intermediate state sample entered a mixed phase state, characterized by
coexisting macroscopic sized regions of superconducting and spin density wave
(SDW) regions, below T_c ~ 0.87 K. These data were analyzed using a
back-to-back cutoff exponential function, allowing the extraction of the first
three moments of the magnetic field distribution. Formation of a vortex lattice
is observed below 0.87 K as evidenced by the diamagnetic shift for the two
fields in which we took intermediate state data.
