Nothing rare about it. Now it is maybe but I have used this same machine not only at Golds in Venice but also in gyms in Washington state and Tennessee as well. Not that unique. The hip sled and hack squat mAchine are better anyway. This one Arnold is using made your hip flexors work harder than the targeted muscles.
Well perhaps this one in the picture is a little rare. It's the only one to
ever be installed in the
original Golds Gym on Pacific Avenue and used by ARNOLD, Columbo, Corney, etc. and then it was installed at Golds Gym on Hampton Drive and used by most of the late 80's and 1990's bodybuilding champions Platz, Wheeler, Cormier, Baker, Priest, etc. Eventually making it's way to Golds Las Vegas.