A PRESTIGIOUS office building at 1 College Green, Dublin 2, is expected to make in excess of £2 million when it is auctioned on May 27th by Lisney. The 13,176-square-foot building is currently occupied by stockhrokers Riada and Co, which is shortly to relocate to the International Financial Services Centre along with its holding company, ABN Amro Bank. The College Green building and the bank premises on St Stephen's Green were acquired by Brian Rhatigan's development company in part exchange for a new 42,000-square-foot block the bank is to occupy at the Custom House Plaza in the IFSC. Number 1 College Green is a seven-storey building over a secure archive and storage basement. The block was modernised by New Ireland Assurance in 1990. There is a board room suite at pent-house level.