Announcements of the closing of Bob Slate Stationer were posted Thursday morning. This one was in the door of the Porter Square site. (Photo: Marc Levy)

The owners of three Bob Slate Stationer stores in Porter and Harvard squares are giving up on selling them and closing them outright, co-owner Mallory Slate said Thursday afternoon.

Fliers announcing the move were put in a store windows or doors at 9 that morning.

There remain “a couple of potential candidates” for buyers, co-owner Justin Slate said Friday, and there was still hope of a “last-minute” sale.

The Bob Slate stores have been for sale since October 2009, more than 45 years after Mallory and Justin Slate took over the stores from their father, who began selling stationery in Harvard Square 78 years ago.

“The next owner will take over a healthy, vibrant business situation operated by a superb, dedicated staff being guided by a strong and committed management team,” the brothers said when the sale was announced. Although the stores were said to be profitable, the announcements posted Thursday acknowledged “declining sales” as well as advancing age.

In October 2009, though, the decline wasn’t enough to discourage the brothers in their search for a new owner.

“This is probably not a situation for a national chain with their homogenized approach to retailing,” Mallory Slate said at the time. “It’s all about finding the right buyer.”

There were candidates for a purchase since the process began in October, but the Slate brothers and buyers couldn’t come to a mutual agreement, Justin Slate said Friday.

While it was never specified how much time was allotted to find the perfect buyer — a task still being handled by Walter Huskins, of Ridge Hill Partners Inc. in Needham, if a buyer yet comes forward — it seemed to run out Thursday morning.

The three stores are in Harvard Square at 63 Church St. and 1288 Massachusetts Ave., and in Porter Square in a family-owned building at 1975 Massachusetts Ave. In addition to typical stationery supplies, the stores sell calendars, boxes, small gifts, puzzles and toys, and office and mailing supplies.

“I knew it was for sale, but this is a great shock,” said historian Charles Bahne, a regular customer at the Church Street store. “There’s no other place you can get what they have.”

Another thing that worried him, he said, was what would happen to the stores’ employees, many of whom the brothers “have had as long as I can remember.”

When the sale was announced, the Slates called their workers “an integral part of the company” and said “the new owner would be wise to keep and utilize the talents of the team. Mallory and Justin do not anticipate any changes.” The new fliers also thank them warmly for their work.

A closing sometime in March is referred to in the fliers, which note that leases on the Harvard Square properties have expired and that while the landlords “have been supportive and patient, they are actively seeking new tenants.” The Porter Square property on its own, the brothers say in their fliers, cannot stand on its own; it has been serving as “logistical support” for the other stores.

A message was left Thursday afternoon with Huskins.

This post was updated Feb. 11 with Justin Slate’s comments.