Securities and Exchange Commission Chairman John S.R. Shad this month broke the longevity record for that office. The former E.F. Hutton executive was appointed on May 6, 1981. No SEC chairman has ever served the full five-year term.

Shad, whose departure has often been rumored, offered his standard reply that he had "no plans beyond lunch next week." Meanwhile, he is scheduled to address the National Press Club Dec. 11 on major issues affecting the securities markets.

Commissioner Joseph A. Grundfest, 34, was sworn in last week as the 65th member of the SEC since it was created in 1934. The nomination of Edward H. Fleishman, 53, to fill the remaining vacancy is before the Senate Banking Committee. However, at the request of Shad, Fleishman participated in a commission meeting this week on the controversial issue of tender offers.

SHAREHOLDER PROPOSALS . . . The SEC has had to back down on its efforts to curb what it considers nuisance proposals at annual meetings by gadfly or activist shareholders.

In the summer of 1983, the agency increased from 3 to 5 percent the percentage of affirmative shareholder votes needed before a proposal could be submitted for a second time. And for submission a third time, a proposal would need an 8 percent approval of shareholders, instead of the previous 6 percent.

On Sept. 13 U.S. District Court Judge June L. Green ruled against the agency in favor of the United Church Board for World Ministries. She ordered the commission to return to the previous rules. The SEC is considering whether to try again next year.

MISSING SECURITIES . . . Since a General Accounting Office investigation showed that only 1 percent of the million stock certificates, worth $5.4 billion, that were lost or stolen between 1978 and 1982 were ever located, the SEC wants to tighten up the procedures.

Henceforth, any broker handling a transaction over $5,000 must check with the SEC to see if the certificates were lost, stolen or counterfeited. The previous limit was $10,000.

Banks and brokerages also would be required to report lost or stolen bond coupons, registered government securities and other securities that do not bear an industry identification number.

MORE OVERSIGHT? . . . Price Waterhouse, one of the so-called Big Eight accounting firms, has been circulating a draft proposal calling for legislation to increase oversight over the profession, following criticism of the industry on Capitol Hill. Rep. John D. Dingell (D-Mich.) has been holding periodic hearings on a number of issues involving accountants, including what their responsibility should be in failures of public corporations that have received a clean bill of health from them.

After similar hearings seven years ago, the American Institute of Certified Public Accountants created a public board that oversees AICPA peer reviews of accounting firms every three years. Price Waterhouse would double the five members and merge the board into a self-regulatory organization under the oversight of the SEC.

AICPA's president, Philip Chenok, called the proposal duplicative and said it would create "a far-reaching authority over American business."