The study „The Pērkone Sub-dialect” by a student of the Department of Baltic Philology Emma Valtere, (1902–1987) at the Library of the University of Latvia dates back to 1935 and is the first description of the Pērkone sub-dialect organised in a specific system and based solely on the author's own authentic collection in the mid-1930s. In 1938, the description was published almost in its entirety in volume XVIII of the collection “Filologu Biedrības Raksti”. The article identifies differences in the content of the two texts, which may affect the information and knowledge available to researchers about the features of the Pērkone sub-dialect. The inclusion of E. Valtere's collection in EH I-II has been analysed, 30 manuscript sub-dialectal words not included in the FBR publication are studied in depth in the context of the lexis of Lower Kurzeme sub-dialects, to reveal the distribution of lexemes and their variants in the neighbouring dialects.