1993 INVERTED CENTER STAMPS OF THE WORLD CATALOG, by Martin Sellinger.  A checklist and value guide for all inverted center stamps.  Prices are way out of date, but it's still a great reference for inverts.  1993, 24 pages, 4 pages of B&W illustrations, stapled card covers, new but perhaps with minor cover blemish from storage. Size: 6" x 9".