Boston-based Hamilton Co. has purchased Captain Parker Arms, a 94-unit multifamily complex in Lexington, for $31.6 million.

The complex had gone on the market just once before in its 40-year history, held by the original developer for all but the last four years. It represented a rare opportunity to acquire a class B property in a town with extremely limited mulitfamily stock, said David Ross, executive vice president at NAI Hunneman, which brokered the transaction for seller Avalon II Massachusetts Value 1 LP.

“The location near the center of town and the high school, and the amenities in Lexington, are what made it so special,” Ross said. “And being a class B property, it was affordable.”

More than 40 potential buyers toured the property and 25 put in bids, ranging from national real estate companies to small and regional players.

The interest reflects the continuing demand for affordably priced multifamily stock. The sales price averages $336,000 per unit. Current rents range from $1,800 to $2,600.

The sellers spent more than $1 million on capital improvements in the last three years.

“These well-developed, managed and maintained buildings will continue to meet the moderate-priced housing needs of the residents in Lexington and the surrounding communities,” Carl Valeri, president of Hamilton Co., said in a statement.