Baltimore Bancorp, one of Maryland's largest bank holding companies, yesterday offered to buy John Hanson Savings & Loan of Greenbelt for $28.8 million in cash, or $12 a share.

If the offer is completed, Baltimore Bancorp would acquire John Hanson's $600 million in assets and 20 branch offices, giving it a total of 50 branches throughout the state.

The offer, which is contingent upon Hanson withdrawing a public offering of its common stock that it began this month, could allow Maryland to retire $11.3 million in notes that the state gave Hanson last summer to boost the S&L's assets, officials at Baltimore Bancorp said.

Hanson needed the notes to qualify for federal deposit insurance when Maryland's state insurance system for thrifts collapsed under the weight of the state's S&L crisis last spring.

Charles Dukes, Hanson chairman and chief executive, would not comment on the offer, except to say that Harry Robinson, president of Baltimore Bancorp, is "a man who knows a good thing when he sees it."

Hanson's board of directors will meet today to consider the proposal, Baltimore Bancorp officials said.

Baltimore Bancorp's primary holdings are the Bank of Baltimore and the Municipal Savings and Loan Association. With the acquisition of Hanson, its assets would climb to $2.7 billion.

Baltimore Bancorp directors approved the offer yesterday and immediately presented it to Hanson. "I hope its a friendly offer," Robinson said. "That's how we meant it."

If Hanson accepts the proposed merger, it then will need the approval of state and federal regulators. Federal Home Loan Bank Board officials said they were not familiar with the offer. Maryland officials could not be reached for comment.

Since last May, when reports of mismanagement at one Baltimore thrift sparked runs at several savings and loans in Maryland and prompted Gov. Harry Hughes to impose a $1,000-a-month withdrawal limit on customers at Hanson and other institutions, Hanson customers have withdrawn at least $35 million from their savings accounts.

That required the $11.5 million in notes from the state so that Hanson's net worth -- its assets minus its liabilities -- would be high enough to qualify for insurance by the Federal Savings and Loan Insurance Corp., the federal agency that insures S&Ls.