Abstract: An adaptor attachable to the watch casing of a watch is structured with attachment means for being secured to the watchband securement means of the watch casing, and is further structured with watchband retaining structure which allows attachment of a watchband by means different than is provided on the watch casing. Thus, the watch casing may be converted for use with watchbands which are not configured to be attachable to that particular watch casing. Likewise, conventional watches employing pin means for attachment of the watchband may be converted to attach uniquely designed watchbands configured for attachment only to correspondingly unique watch casings.