Sentence:  Indeed, so ubiquitous are these <WSD>'sowei</WSD> masks' that they form a veritable Sierra Leonean 'object diaspora' and have become iconic of the region—a <WSD>sowei</WSD> mask, for example, appeared on one of the first series of postage stamps issued by the newly independent Sierra Leone in 1961. 
Meaning of the word marked with <WSD> tags:  A guardian spirit of a Sande society of the Mende, who is represented by a special helmet-like mask.