  We have investigated the properties of cleaved SmB$_6$ single crystals by
x-ray photoelectron spectroscopy. At low temperatures and freshly cleaved
samples a surface core level shift is observed which vanishes when the
temperature is increased. A Sm valence between 2.5 - 2.6 is derived from the
relative intensities of the Sm$^{2+}$ and Sm$^{3+}$ multiplets. The B/Sm
intensity ratio obtained from the core levels is always larger than the
stoichiometric value. Possible reasons for this deviation are discussed. The B
$1s$ signal shows an unexpected complexity: an anomalous low energy component
appears with increasing temperature and is assigned to the formation of a
suboxide at the surface. While several interesting intrinsic and extrinsic
properties of the SmB$_6$ surface are elucidated in this manuscript no clear
indication of a trivial mechanism for the prominent surface conductivity is
found.
