The 'orbs' are circular postmarks made with steel implements whose principle characteristic is that they possess two or more concentric outer rings. These were used in only a few of the larger cities. They were first introduced in the early 1890's and their use continued to as late as the early 1970's. Initial work on classifying the orb postmarks was done by Jim Miller, and the naming conventions used to distinguish the orbs were defined by him. We have studied available material carefully, and with only a few adjustments, have adopted Miller's classification here. Many of the orbs were produced by Pritchard and Andrews, and proof impressions were often taken. We have used these where available. We are actively seeking reports (in the form of 300dpi scans) of dates of use of all of the orb postmarks.

For clarity we have included measurements of the diameters of each ring. These measurements were done electronically on blown-up high resolution scans, and are quoted to the nearest quarter millimeter. Because of inevitable imperfections in the original photocopies and scans of the postmarks, as well as the width of the lines, one should take these measurements as only a guide. In any case, it would be very difficult to obtain such precision on actual on-cover examples.

A complete pictorial database of all orb postmarks is available here to members...