I wasn't aware of a specialized version so Googled the difference......so for anyone else who may not know;
The First Edition (1986): Published as a loose-leaf catalog in an A4 binder, the 1986 edition covers the entire British bronze penny series from 1860 to 1970. It introduced a unique cataloging method using obverse and reverse illustration combinations (e.g., Gouby BP 1860G) along with rarity ratings. [1, 2, 3]
The "Specialized" Editions: In contrast, Gouby later broke the comprehensive 1860–1970 range down into expanded, multi-volume "Specialized" editions (such as the specialized catalog covering just the years 1860 to 1901). These specialized A5 binder editions provide significantly deeper die-variety analysis, highly detailed enlargement photos, and die-pairing values across four distinct grades.
Because the original 1986 book was an exhaustive overview covering a 110-year period, it provides the macro-view of the entire series. The specialized editions zoom in on specific eras to help advanced collectors identify rare die varieties, striking errors, and distinct obverse/reverse collar types.