Greater Bay Bancorp of Palo Alto, Calif., said it would buy Bay  Commercial Services in San Leandro for at least $25.5 million of stock. 
The transaction-valued at 2.06 times Bay Commercial's book value and  17.3 times its earnings-would help Greater Bayexpand in the East Bay area. 
  
Bay Commercial is the $144 million-asset parent of Bay Bank of Commerce,  which has branches in San Leandro, San Ramon, and Hayward. 
Greater Bay would issue 0.7134 share for each outstanding share of Bay  Commercial-if its average closing price is between $27 and $31 per share   when the deal closes. That would value the deal at $25.5 million to $29.2   million.     
  
The purchase, announced Monday and expected to close in the fourth  quarter, would boost Greater Bay's assets to $2.1 billion.