Yes indeed... nice find and contribution to this forum X1.
These are interesting structures based around the Purcell - ie an adjustable slide and grip hitch (however, instead of a double strand, its built around a single strand). I use the Purcell in many applications - eg as an energy absorbing fall-arrest lanyard when undertaking activities at height. This might have applications as a foot stirrup in rope ascending techniques (as an example).
Mark