Journal of L.M. Montgomery Studies (the life and work of the famous author of Anne of Green Gables)
Technical Bulletins of the Williamstown + Atlanta Art Conservation Center
Archiv Orientalni, 1929-2010. Later known as ArOr: Quarterly Journal of African and Asian Studies. Partly indexed by JURN via the URL kramerius.lib.cas.cz/periodical/ — which is not ideal, in terms of either target or Google Search’s current indexing, but is the best that can be done at present.
WIPO Magazine (World Intellectual Property Organisation, JURN was already indexing the WIPO Journal).
Quantitative Science Studies (MIT, “theoretical and empirical research on science and the scientific workforce”)
Philosophy of Medicine
Luminaria (interdisciplinary natural biology, Brazil, latest issues are partly in English)
Three more UK repositories, and the per-article record pages of IA Scholar at fatcat.wiki/release/ (the latter fairly poorly indexed by Google Search, at present).
Initial harvest of ISSNs is now integrated into the openECO directory. The process of adding ISSNs is not yet complete.