During the summer of 1972, the Maryland State Racing Commission refused to let a Baltimore law clerk look at public documents listing owners of the Marlboro Race Track, according to testimony in court today.

Charles Tatelbaum, the attorney who dispatched the clerk to commission headquarters, testified at the political corruption trial of Gov. Marvin Mandel that the racing authorities told his clerk to produce a letter explaining why he needed the information.

Tatelbaum said he had to threaten to "go to the office of the attorney general" before the commission would release any information and then it was a typed list of owners rather than access to public documents.

The degree of secrecy that cloaked purchase of the Marlboro Race Track is crucial to the current phase of the federal government's case against Mandel and his five friends and codefendants W. Dale Hess, Harry W. Rodgers Ill, William A. Rodgers, Ernest M. Cory Jr. and Irvin Kovens.

Hess and the Rodgers brothers secretly purchased the track with Cory and, allegedly, on Dec. 31, 1971, with Kovens, The prosecution contends that Mandel knew his friends owned the track and that he influenced legislation in order to bring profits to the race course. In return, the prosecution charges, Mandel received about $350,000 in gifts and favors.

The testimony of the Baltimore attorney followed lengthy testimony from state senators about maneuvers at the state legislature during the 1972 session.

Sen. Julian L. Lapides (D-Baltimore) completed his testimony today by explaining why he had sponsored legislation requiring full disclosure of owners of race tracks.

Because the state determines racing days for tracks - days are the currency of business - Lapides said he felt it should be publicly known who would receive days from the state before they are parceled out.

His first disclosure bill was passed in 1969. But when the racing commission ruled the law was too vague to require full disclosure of all owners who would benefit, he sponsored along with his Senate committee a new bill, which passed in 1974, according to testimony today.