Martin Gengerke notes: Includes Hollinbeck Stamp & Coin Co., Hollinbeck-Kagin, and Kagin's. Initially Arthur M. and Paul Kagin, later Art & Don Kagin. Most of the missing sale numbers were included in the immediately preceding catalogs as "double" sales, the reason later being given that their sales were twice as large as others of the period. History bears this out as their sales did indeed have more than twice as many lots as the the national average for that period. On the other hand, their 250th and 309th (1977 ANA) sales each had several separate volumes, with only one sale number assigned.
Kagin's website is https://kagins.com/.
Newman Portal acknowledges Dan Hamelberg for loaning his extensive reference set of Kagin's auction catalogs for scanning.
Data source: content provided by auction company.