I have no idea where the 1685 came from. On the other hand, https://portal.opentopography.org/raster?opentopoID=OTSRTM.082015.4326.1 gives 1716, from SRTM scanning. Wikidata has 1667, quoting Wikipedia (which is questionable), and Wikipedia links to https://web.archive.org/web/20141031094927/http://summitcheeseburger.com/summits/country/NA/Namibia, which is hardly a reliable source either. I don’t intend to criticise you, it was just a question.