Irvin Kovens, millionaire political fund raiser and close friend of Maryland Gov. Marvin Mandel, personally guaranteed payment of most of Mandel's separation and divorce settlement with Barbara Mandel, according to evidence presented in the governor's trial today.

The once secret divorce settlement now appears to be worth at least $400,000, after it was learned today that Mandel gave his former wife $39,062 in September, 1974, and agreed to pay her $1,562 each month for three years beginning in August 1974.

Mandel, who takes home about $17,000 annually from his state salary also provided his former wife with a new luxury Buick as part of the settlement, sources said.

With her receipt of Koven's guarantee and his promise of $135,000 worth of tax-free bonds at the time of the divorce, Barbara Mandel finally left the Governor's Mansion in December 1973, according to evidence presented today.

Kovens figures in the Mandel political corruption trial as the alleged secret majority stock holder of the Marlboro Race Track, a now defunct half-mile course in Prince George's County which the prosecution claims profited from legislation backed by the governor.

Apart from today's testimony, which showed that Kovens gave Barbara Mandel first $135,000 and later another $20,000 worth of tax-free bonds, further details of the secret divorce settlement emerged today from sources. Pieced together with previously reported items, they showed the agreement provided Barbara Mandel with:

A $39,062 payment one month after the August, 1974, divorce decree.

Monthly payments of $1,562 for three years from the date of the decree.

A new air-conditioned luxury Buick sedan.

A $100,000 life insurance policy on the governor as well as a health insurance policy.

$155,000 worth of tax-free bonds issued by Calvert County.

About $73,000 in the initial property settlement from the governor's savings account.

$25,000 interest in a leasing firm founded by her family.

Barbara Mandel was not called to testify today as had been expected and may not be called at all during Mandel's retrial. Prosecutors and the lawyer for Barbara Mandel reached an agreement under which certain documents would be turned over to the government without the necessity of her testifying about them.

With Kovens' inclusion in this trial he was excused for health reasons from the first trial that was aborted last December, the highly personal and private divorce settlement has become a centerpiece of the corruption case.

In its multi-count indictment, the government alleges that Mandel accepted some $350,000 worth of gifts from his codefendants as bribes. Many of the gifts, according to evidence had gone to pay the expensive divorce settlement hardly manageable with the governor's take-home salary of $17,000.

The government alleges in its multicount mail fraud and racketeering indictment that Mandel, in return for these gifts, lobbied for legislation that brought profits to the businesses of his codefendants: Kovens, W. Dale Hess, Harry W. Rodgers III, William A. Rodgers and Ernest M. Cory Jr.

The first witness to set the stage for the bond transaction was Kovens' Hagerstown stock broker, Joseph H. Bagenais.

Bagenais testified that he sold Kovens $175,000 worth of Clavert County bonds guaranteed by Baltimore Gas & Electric and made payable to the bearer.

The bonds themselves were introduced into evidence and their serial numbers corresponded to those listed in the divorce settlement documents for Barbara Mandel.

Susan Flater, a former bank teller, called to the witness stand, nervously described how Barbara Mandel regularly came to her bank and clipped coupons from the county bonds.

During her testimony, chief federal prosecutor Barnet D. Skolnik produced the guarantee from Kovens and two official letters signed by Barbara and Marvin Mandel covering their divorce settlement.

"Whereas, the Guarantor (Kovens) desires to assist Marvin and Barbara Mandel in the negotiation andexecution of an Interim Agreement, a Lump Sum Agreement and a Separation and Property Settlement Agreement," the document began, ". . . (he) guarantees the performance by Marvin Mandel . . . of the obligations imposed upon him . . ."

The document then listed items not included in evidence because of the private nature of the settlement.

That guarantee was dated Dec. 19, 1973, the same day as one of the two letters and the same day that Barbara Mandel gave up her stubborn six month vigil to win back her husband.

He had left the mansion in July, 1973, proclaiming he loved another woman, Jeanne Blackistone Dorsey. Mandel wed Jeanne hours after his August, 1974, divorce.

When the first lump sum payment became due, Mandel - fresh from a European honeymoon that required a secret $10,000 loan - received a $42,000 laundered loan from the Catholic Pallottine Fathers to meet his obligation, according to testimony this week.

The majority of his divorce debts were shouldered by Kovens, who is known as the most influential political boss in the state and the chief campaign fund raiser for Mandel.

Mandel's public financial disclosure statements have never shown the support he received from Kovens.

But Kovens' name is often omitted from public documents. One of Kovens' business partners, Irving T. SchwartzM testified today that he acted as a front man for Kovens in two businesses.

It is alleged by the government that Schwartz also fronted fro Kovens in the Marlboro Race Track.

Kovens also has an interest in Mondawmin Shopping Mall in Baltimore, the site of a proposed state-funded subway stop and of a branch office of the state Motor Vehicle Administration.