I've seen dies like this before but never with the adjuster. I imagine the basic die is set to cut slightly undersize and the adjuster used to set the fit required. Setting will be retained when the die is removed from the diestock.
With a normal die the adjustment is lost when the die is removed so for precise work it has to be reset each time. If you want to retain adjustment between uses with a normal die you need to make up a carrier with the requisite screws and leave the die in that. Geo. H. Thomas advocated this and published designs for his set.
Wonderful idea but a set of such carriers another project I shall never get round to.
Clive.
Edited By Clive Foster on 26/02/2017 13:24:18