"It is out there," one industry professional tells GlobeSt.com, with the source supporting other claims that Eastdil Secured has been hired to trade the 21-story property. Besides being in the heart of Boston's Financial District, a long-term lease to Brown Brothers Harriman has observers anticipating a substantial price will be needed to nail down 50 Milk St., a figure that could exceed $150 million. The current ownership, a private trust from Hawaii, paid $123 million for the asset. Officials at Eastdil declined comment, while efforts to contact the owners by press deadline were unsuccessful. Nonetheless, sources insist 50 Milk St. is on the block.

The previous sale of the tower in 2005 created a financial buzz, with a foreign investment client of locally based Barrington Capital Partners reaping $447 per sf after another short-term hold. At the time, the $400-per-sf threshold was a lofty level locally for that type of asset, and well above the $109 million--$396 per sf--the Australian investor had paid for in 2002. If the $150-million mark is attained, the per sf price would be $545, and would approach three times the amount 50 Milk St. sold for in 1997 when it fetched $55.5 million.

While that would be a stratospheric accretion over just one decade, the pricing premonitions do have support considering the recent rates achieved in Greater Boston's hyperactive sales market. Not only are major towers now garnering more than $800 per sf, plenty of investors are on hand to drive rates up for ancillary assets such as 50 Milk St. The one-time Boston cow path itself has seen plenty of investment action this year, with the aforementioned 45 Milk St. selling for $33.9 million in June to a foreign investor, or about $490 per sf. A few blocks down, 147 Milk St. was purchased this spring by Lexington Realty Trust for $20 million, a $382-per-sf mark for the 10-story, 52,000-sf office building.

As previously detailed by GlobeSt.com, the generous square footage rate achieved in the 45 Milk St. transaction has lured numerous small- and mid-sized Boston buildings to the sales block. In some cases, those properties are also receiving robust attention, although some brokers maintain 45 Milk St. was an anomaly because the Grade A tenant roster and strong leasing history belie its class B constitution. And 50 Milk St. is "in another category altogether," says one source who predicts the stable tenant roster, first-class quality and an irreplaceable location will translate into a substantial bump from the last sale. "That building is a true gem," says the source. The sellers "will do quite well."