In a further attempt to remain independent, Washington's Security National Bank yesterday used a five-page letter to tell its shareholders why they should not accept a tender offer by NS&T Bankshares.

Yesterday's letter, signed by Security Chairman Robert K. Koontz Jr. and President Thomas J. Schaefer, painted NS&T's offer as an attempt to draw stockholders from the security of solid profitability into the uncertain world of corporate finance. Sent to all stockholders, the Security letter criticized both the price and the character of the NS&T offer.

Security, the city's eighth-largest bank, has bitterly resisted NS&T's Aug. 4 offer to buy up to 100 percent of Security's shares at $62 per share. To ward off the hostile takeover, Security had announced July 22 that it would merge with the smaller Washington Bank. That announcement followed Security's rejection of a bid from James Madison Ltd., parent company for Madison National Bank, to pay $60 a share for up to 44 percent of Security's stock.

NS&T's offer expires at 5 p.m. Sept. 14.

The letter criticized the $62 price as too low in light of Security's prospects for profitability. Not only do current trends in earnings and dividends point to higher share prices in the future, said the letter, but new innovations such as automated banking services should further enhance profits in the near future. The document cited the Security board's Aug. 13 decision to raise the quarterly dividend from 45 cents to 70 cents, and it pointed to per-share net income that went up 34 percent for the first half of this year.

NS&T, the parent company of National Savings and Trust Co., last week argued that the $62 price was 70 percent above the shares' book value as of June 30.

Yesterday's letter also argued that uncertainty over whether NS&T will be able to purchase the shares could mean that tendering shares is a very risky proposition.

The letter pointed especially to a provision in NS&T's offer that if less than 40 percent of Security's shares is tendered, NS&T is under no obligation to purchase any.

Moreover, the letter continued, NS&T has obtained neither the required regulatory approvals nor the financing necessary for the takeover. The regulatory approvals could take four to six months, and "depending on the circumstances -- e.g. an interested party's intervention in a regulatory proceeding -- might well be significantly longer," the letter said.

The result in either case could be that Security shareholders who tender their shares could find them tied up for months and then returned, the letter said.

Security's letter also questioned NS&T's ability to maintain its profitability while servicing the funds necessary for the shares -- more than $24 million for the bank's 400,000 shares outstanding.

As one means of combatting the takeover, more than 30 percent of Security's shareholders have signed an agreement under which they pledge the right of first refusal to another member of the group if they decide to sell their shares at NS&T's offered price.