M Goldshteyn is a pseudonym for Moyshe Bershling (1900?-1941), who was born in Piaski. He later lived in Łódź and Bialystok, where he worked as a Jewish history teacher. He was an organizer in the Linke Poale-Tsiyon (leftist workers of Zion), and cofounded an organization devoted to the colonization of Birobidzhan. He wrote poems for numerous publications. He was arrested in Bialystok in July 1941, and was never seen again.
Source: Congress for Jewish Culture