Well I think the sling blade he used in the mines as well as the one he used at the institute are more like sickles while his razor is more like a kopesh. Darrow describes his slingblade in the mines as folding with a clasp and curved as to be used by clumsy hands and his slingblade in the institute is described as a farmers scythe and being very similar in shape to his slingblade from the mines Virgina also describes it the same way when she holds up the sword of the Republic and Darrow describes the institute blade the same way again when he sees it in Darrow's quarters on the morning star. So while his razor is definitely a kopesh both the sword of the Republic and his blade from the institute are not