The Stoney Point Chamber-All Bullet Comparator body attaches to the blade of your caliper with a small thumbscrew and utilizes inserts for each caliber. The design of this tool allows proper alignment when used with the stoney Point Chamber-All OAL gauge (offset position), or it can be used in a conventional centerline method. Inserts are sold separately, or the tool can be purchaed with six inserts as a kit. The body can also be used with to hold the Stoney Point headspace gage inserts.
Big Book Catalog, Issue:66, Page:513
Sinclair, Issue:3B, Page:035