By the time the doors opened, there were 28 people—not counting the kid in the stroller—in line. That wouldn’t have seemed very many if the queue had been for Billy Joel tickets or the premiere of Harry Potter and the Prisoner of Azkaban. But the people lined up outside downtown’s Gallery at Flashpoint at 6 p.m. Thursday, May 13, were there to buy art. And not just any art, but Washington art.

Inside were 100 pieces, one by each of the participating artists, for sale for $500 each. They were—or were supposed to be—2 square feet or smaller. Their contributors included some established local notables, including Colby Caldwell, Judy Jashinsky, William Newman, and Robin Rose, as well as such rising stars as Iona Brown, Dan Steinhilber, and Tim Tate. But buyers had to do more than get there early to purchase a work by a particular artist. They also had to know his or her style well enough to identify it without guidance. That’s why the show was titled “Anonymous.’’

It’s impossible to know if the artworks would have sold faster or slower if they had been labeled by artist during the week they were on display before the sale. But Washington Project for the ArtsCorcoran Executive Director Annie Adjchavanich, who organized the show, reveals that at least one piece that moved quickly was widely misidentified.

The first pieces to sell were not by any of the luminaries named above. They were Mary Early’s three-dimensional, yellow construction of beeswax and wood; Andrea Haffner’s steel, resin, and pigments piece, with two hanging circles containing fertility imagery; and Kevin A. Kepple’s patterned abstraction, red and milky white, made of glue and ink on birch.

The show, which remains open through June 4, includes plenty of paintings and photographs, but has more glass works and inkjet prints than most museums of contemporary art. A handful of the 100 offerings are purely conceptual, including one that bills itself as a smart deal: a framed winning Maryland Lottery ticket, worth $1,000 but available for half that figure—a little Duchamp for the Las Vegas Age.

The terms of sale are essentially cash-and-carry. Buyers must be present to make a purchase—although proxies are allowed—and must pay on the spot. Some of the rules, such as the one warning that “no line disputes will be tolerated,’’ proved unnecessary with the overwhelmingly genteel first-night crowd. But two people were serious enough about getting the work they wanted that they hired Corcoran students as place-holders at $10 an hour; the first of the line-sitters arrived at 8 a.m, 10 hours before the sale began.

The WPAC will divide the proceeds 50/50 with the artists, although a few of them have donated their share of the money to the organization. The WPAC’s take will benefit the programming fund of the organization, which Adjchavanich says has grown to more than 1,000 members from fewer than 100 when she started there three years ago.

More such WPAC shows are likely, Adjchavanich notes, although some tinkering with the concept may be done. “The 2-by-2 format seems to work,’’ she adds, even if a few artists ignored it. “Not everyone reads,’’ she shrugs.

When the opening evening was over, 28 artworks had sold, and another five went on Friday. Yet some eminently collectible pieces remained for sale. The show still has works available by such artists as—oh, but that would be telling. —Mark Jenkins