Never seen this type before, and cannot find anything about them on the "internet".
That is why I used the word rare.
They slide easily, lock up tight, and are well made.
Imported by R CALUWAERTS CO inc N.Y.
Trying to decide to keep or sell.
Sure is different that's for sure.
Those are slick ! They look like they may be even easier to use than the standard Channel-lock slip joint style.