Gov. Marvin Mandel, in a letter signed in his hospital room today, announced that he will transfer the constitutional duties of his office to Lt. Gov. Blair Lee III for exactly two hours Tuesday so Lee can sign 56 bills enacted by the General Assembly and approve Easter commutations for about 200 state and local prisoners.

Mandel's decision to limit the time and authority for which Lee will be "acting governor" prompted some observers to comment that the ailing governor is apparently reluctant to give up much of his power, despite an illness that could limit his work load until summer.

Lee accepted the assignment in good humor, however, adding that he had suggested the two-hour time limit in a talk with Alan M. Wilner, Mandel's chief legislative officer.

"That's not even time enough to appoint a judge," said one legislative leader. "And if that's not bad enough, he carefully spelled out what Blair could do."

But Lee said he is "completely satisfied with the arrangement. I suggested the two hours."

Lee joked that "I can raise more hell in two hours . . .Why, I've asked for a list of vacancies, and have told the department chiefs that heads may roll."

Mandel sent a letter today, released at 3 p.m., designating Blair as "acting governor" for a two-hour period Tuesday (10 a.m. until noon).

Mandel sent a letter today, released advised me that there are approximately 56 bills and joint resolutions, including a number of emergency bills, that have been reviewed by him and by the attorney general, and are appropriate for signature.

"In addition, prior to my hospitalization I had determined to issue an Easter commutation to state and local prisoners meeting certain criteria. A list of approximately 200 such inmates satisfying those criteria has been prepared by the Division of Parole and Probation. It is important that these commutations be issued in order to help relieve some of the overcrowding in the correctional facilities."

"As soon as the doctor approves, I would like to meet with you to discuss how we will proceed until my release from the hospital," Mandel wrote.

Lee had said earlier today that "the beauty of the acting governor statute is that is is a designation that can be turned on and off like a water tap, for 30 minutes, or two hours or six hours, whatever the need."

Lee added that he sees "no need to set up an elaborate mechanism" for operating the executive branch in the next 10 weeks so long as the acting governor designation is available.

Tuesday's bill-signing session, Lee said, includes mostly "rather unimportant local bills," but "the hitch" in postponing the ceremony - which is traditional for the day after the legislature but not mandated by law - is that four or five of the bills are designated as emergency measures, which means they become effective the moment they are signed.

Lee said that the governor normally signs bills on three or four separate dates between the end of the legislature and the May 31 deadline, "with the tougher ones held to the end."

Another tradition, begun under the administration of Gov. Spiro T. Agnew and expanded by Mandel, is a day-long hearing on bills that certain individuals and groups think should be vetoed.

Whether Mandel will be well enough to stand up to the rigors of that day-long process is not yet known. "We'll play it by ear, depending on his improvement," Lee said.

The lieutenant governor spent part of today watching proceedings of the House of Delegates from his favorite observation post, the glass-enclosed television booth high in the gallery.

Both the House and the Senate raced to conclude consideration of bills today so they could avoid working on Easter Sunday. The assembly's session ends at midnight Monday.

The major issue still unresolved is House consideration of the capital budget, which includes funds for the purchase of an abandoned Continental Can Co. factory in East Baltimore as a prison site.

The prison site, which was the subject of a filibuster before its passage in the Senate, was apparently the focus of a deal today involving a bill that would increase state aid to public education.

The Senate Budget and Taxation Committee at first voted 7 to 5 against the proposal, which would provide $13 million in general aid to the local school systems, including nearly $3 million to suburban Washington districts.

Later today, after intense lobbying by delegates from Montgomery and Prince George's counties, the committee reversed itself and gave the bill a favorable report, making its passage likely.

Sen. Victor L. Crawford (D-Montgomery), a committee member who voted against the bill both times, said "You know what the quid pro quo was? It was Continental Can."

Crawford explained that some members of the Prince George's House delegation threatened to vote against that appropriation unless Sen. Roy N. Staten, chairman of the budget committee, reversed the original unfavorable report on the school aid bill that those same Prince George's delegates wanted so badly.

Del. Gerard F. Devlin (D-Prince George's), who will vote the Continental Can appropriation, said "I certainly would have reversed my position" if the aid bill had been killed.

"It means everything to Prince George's, and Continental Can means nothing," said Devlin.

"It certainly was a consideration" in the turnaround by the Senate committee, according to Devlin, who was one of three delegates who rushed to Lee's office after hearing of the original defeat of the aid proposal.

It was believed that Devlin, Del. Lucille Maurer (D-Montgomery), the primary sponsor of the education bill, and Del. Frederick C. Rummage Jr., head of the Prince George's County delegation, urged Lee to approach Sen. Staten with the word that the Continental Can site might be in trouble if the decision were not reversed.

"They wanted to know why people like (Senate Majority Leader (Roy N.) Staten (D-Baltimore County) and (Sen. Alfred) Lipin (D-Anne Arundel) were voting against their precious educational plan," said Lee. Staten and Lipin are the two senators who pushed Continental Can through a reluctant Senate last week.

Asked if the Prince George's legislators had threatened to vote against the prison proposal, Lee replied, "That's the way they do things - they'd threaten to do anything."

Late yesterday, responding to the threatened withdrawal of malpractice insurance for lawyers by the largest private insurer, the House passed and sent to Gov. Mandel a bill that would set up a state-operated mutual insurance firm to provide malpractice coverage for attorneys.

The Legal Mutual Liability Insurance Society of Maryland would provide coverage similar to that offered to physicians under a 1975 law. Lawyers who wanted the coverage would pay a $300 fee to join the society and then pay premiums set by the state insurance commissioner.

Earlier this year the Affiliated FM Insurance Co. of Rhode Island announced that it planned to cease offering malpractice insurance for Maryland lawyers at the end of the year. The firm now provides coverage for about half the state's 8,000 lawyers, and is the only firm still writing such policies.

Because the same Rhode Island firm also wants to end malpractice coverage for podiatrists, the Assembly also approved a bill last night that would permit the insurance commissioner to direct private insurers to underwrite malpractice coverage for any professional group that is unable to obtain insurance in the private market.