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We re-examine the extremely metal-poor (XMP) dwarf galaxy AGC 198691 using ahigh quality spectrum obtained by the LBT's MODS instrument. Previous spectralobservations obtained from KOSMOS on the Mayall 4-m and the Blue Channelspectrograph on the MMT 6.5-m telescope did not allow for the determination ofsulfur, argon, or helium abundances. We report an updated and full chemicalabundance analysis for AGC 198691, including confirmation of the extremely low"direct" oxygen abundance with a value of 12 + log(O/H) = 7.06 $\pm$ 0.03. AGC198691's low metallicity potentially makes it a high value target for helpingdetermine the primordial helium abundance ($Y_p$). Though complicated by a Na Inight sky line partially overlaying the He I $\lambda$5876 emission line, theLBT/MODS spectrum proved adequate for determining AGC 198691's heliumabundance. We employ the recently expanded and improved model of Aver et al.(2021), incorporating higher Balmer and Paschen lines, augmented by theobservation of the infrared helium emission line He I $\lambda$10830 obtainedby Hsyu et al. (2020). Applying our full model produced a reliable heliumabundance determination, consistent with the expectation for its metallicity.Although this is the lowest metallicity object with a detailed heliumabundance, unfortunately, due to its faintness (EW(H$\beta$) $<$ 100 AA) andthe compromised He I $\lambda$5876, the resultant uncertainty on the heliumabundance is too large to allow a significant improvement on the measurement of$Y_p$.

A comprehensive chemical abundance analysis of the extremely metal poor Leoncino Dwarf galaxy (AGC 198691)