  The oldest stars in the Milky Way are metal-poor with [Fe/H] < -- 1.0,
displaying peculiar elemental abundances compared to solar values. The relative
variations in the chemical compositions among stars is also increasing with
decreasing stellar metallicity, allowing for the pure signature of unique
nucleosynthesis processes to be revealed. In this work, we report the
atmospheric parameters, main dynamic properties, and the abundances of four
metal-poor stars: HE 1523--0901, HD 6268, HD 121135, and HD 195636 (--1.5 >
[Fe/H] >--3.0). The abundances were derived from spectra obtained with the HRS
echelle spectrograph at the SALT, using both LTE and NLTE approaches. Based on
their kinematical properties, we show that HE 1523--0901 and HD 195636 are halo
stars with typical high velocities. In particular, HD 121135 displays a
peculiar kinematical behaviour, making it unclear whether it is a halo or an
accreted star. Furthermore, HD 6268 is possibly a rare prototype of very
metal-poor thick disk stars. The abundances derived for our stars are compared
with theoretical stellar models and with other stars with similar metallicity
values from the literature. HD 121135 is Al-poor and Sc-poor, compared to stars
observed in the same metallicity range (--1.62 > [Fe/H] >--1.12). The most
metal-poor stars in our sample, HE 1523 -- 0901, HD 6268, and HD 195636,
exhibit anomalies that are better explained by supernova models from
fast-rotating stellar progenitors for elements up to the Fe group. Compared to
other stars in the same metallicity range, their common biggest anomaly is
represented by the low Sc abundances. If we consider the elements beyond Zn, HE
1523--0901 can be classified as an r-II star, HD 6268 as an r-I candidate, and
HD 195636 and HD 121135 exhibiting a borderline r-process enrichment between
limited-r and r-I star.
