Not a Brethren periodical but appears to have followed Dispensationalist lines and been important in the development of pre-Millennialism in North America.Contains articles by CHM, JND, J.Denham Smith etc.Volumes seem to be 6 issues each.
From Fundamentalism and Evangelicals by John Mcmanners, Harriet A. Harris
From Christian Fundamentalism in America: A Cultural History by David S. New
This https://www.forgottenbooks.com/en/download_pdf/Waymarks_in_the_Wilderness_v1_1000519541.pdf suggests it started in 1857 though others say 1862.
Waymarks was published intermittently between 1854 and 1872. For an 1857 copy see: https://archive.org/details/waymarksinwilder00ingl/page