Blue Chip Stamps was first disclosed as a position of Berkshire in its 1972 10-K, as shown below:

[1]
Per the 1973 annual report for Blue Chip Stamps shown below, the following people were on the board of the company, including Warren Buffett and Charlie Munger:


[2]
Directors:
1. Warren Buffett - personal investments
2. Z. Wayne Griffin - Chairman of Community Redevelopment Agency of the City of Los Angeles; real estate developer; personal investments
3. John P. Guerin, Jr. - General partner of J.P. Guerin and Co., investors; director of Pacific Stock Exchange, Inc.; Chairman of the Board of New America Fund, Inc.
4. Joseph P. Hughes - President of Hughes Markets, Inc.; Chairman of the Board of Certified Grocers of California, Ltd.
5. Emmett H. Jones - President of Terminal Oil Company, Industrial Engineering & Equipment Corporation and Westates Investment Co.
6. Donald A. Koeppel - Chairman of the Board and President of the Company
7. Charles T. Munger - General partner of Wheeler, Munger & Co., investors
8. William F. Ramsey - Executive Vice President of the Company
9. Ron Stever - Chairman of the Board of the Stever Companies, consulting actuaries and insurance brokers, and of Crescent Wharf & Warehouse Co.
10. Andrew J. Wolf - President of A & B Supermarkets, Inc.
Sources:
[1] Berkshire Hathaway 1972 10-K.
[2] Blue Chip Stamps 1973 Annual Report.