NEW YORK — Capping a billion-dollar auction week of postwar and contemporary art, boutique firm Phillips de Pury & Company sold a modest $79,904,500 at its Park Avenue headquarters. Modest, at least, compared to the auction giants Christie’s and Sotheby’s, which delivered back-to-back evening sales tallying $887.5 million.

At Phillips de Pury, only 35 lots were offered, with 13 carrying third-party financial guarantees that pretty much pre-sold the big lots in the sale and insured a positive result. Twenty-nine of those 35 sold for a buy-in rate by lot of 17 percent and two percent by value.

The overall total fell in the middle of the pre-sale expectations, which were $73,620,000-110,730,000. That was slightly better than last November’s $71,292,500 sale, which was 16 sixteen percent unsold by lot. Four artist records were set, four lots sold for over ten million dollars, and 15 hurdled the million-dollar mark.

Offering younger, cutting-edge artists is the house’s specialty, and that was apparent early on with Tauba Auerbach’s “Untitled (Fold)” trompe-l’oeil composition from 2010, which sold for a record $290,500 (est. $200-300,000) to New York dealer Alberto Mugrabi.

Next up, Rashid Johnson’s darkly decorative, 98¼-inch-high “Fly” (2011), comprised of branded red oak flooring, black soap, wax, and gold paint went for a record $182,500 to an anonymous telephone bidder (est. $100-150,000). Los Angeles dealer Patricia Marshall was the underbidder on the Johnson, which was also chased by Milan dealer Nicolo Cardi.

In similar fashion, Sterling Ruby’s mural-scaled, 90-by-134-inch “SP 17, 2008,” executed in acrylic on canvas, sold for a record $626,500 (est. $400-600,000) to Los Angeles art advisor Julie Miyoshi of Miyoshi Art Projects LLC.

“Phillips’ estimates are particularly on the high side,” commented Miyoshi as she departed the salesroom, “but I’m happy with my purchase.” The dealer said the work was purchased for an American collector. Milan dealer Cardi of Cardi Black Box was the underbidder.

Dan Colen’s bubble gum-on-canvas “S&M” (2010), complete with a certificate of authenticity signed by the artist, sold for a record $578,500 (est. $200-300,000) to New York art advisor Wendy Cromwell. Greenwich Connecticut collector Peter Brant was the underbidder.

Strong bidding greeting Mark Grotjahn’s colored pencil-on-paper “Untitled (Cream Butterfly Thin Black Lines #673)” (2007), which sold to another telephone bidder for $734,500 (est. $400-600,000). At one point in the bidding, one specialist manning a telephone attempted to split the bid in half on behalf of her client to a $5,000 increment. Auctioneer and Phillips chairman Simon de Pury couldn’t help telling the crowded salesroom, “It’s a measly little increment,” and declined the offer. The anonymous cheapskate on the line buckled and took the $10,000 increment. It last sold at Phillips de Pury London in April 2008 for GBP 90,500/$179,813.

The rather paltry levels of bidding may have been a question of auction fatigue, coming at the end of a long week of evening and day sales. In fact, Christie’s “day” sale was still going strong as Phillips started its evening auction 15 minutes late.

Luckily for Phillips — a closely owned company controlled by the Russian based Mercury Group — had enough third-party guarantees to carry the sale, as clearly evidenced by Gerhard Richter’s huge abstract, “Kegel (Cone)” (1985), which sold on what appeared to be a single bid for a hammer price of $11 million, or $12,402,500 with fees (est. $12-18 million).

The same reception greeted Jean-Michel Basquiat’s early and goofy two-figure composition, “Humidity” (1982), which sold on what appeared to be a single telephone bid for $12,402,500 (est. $12-18 million).

Another Basquiat, a work on paper “Self-Portrait” (1982), elicited spirited bidding even though the fierce and richly colored composition’s authenticity was reportedly challenged earlier in the day, despite the fact that it was accompanied by a certificate of authenticity by the recently disbanded Basquiat Authentication Committee. It sold for $4,058,500 (est. $2.5-3.5 million).

“Luckily we had the wherewithal to prove its authenticity,” said Michael McGinnis, the newly elevated CEO of Phillips de Pury and the firm’s worldwide head of contemporary art.

Another big lot backed by a third-party financial guarantee also drew scant attention as Andy Warhol’s lipstick-enhanced “Mao” (1973), measuring 50 by 42 inches, sold, according  to auctioneer de Pury, to  “a gentleman in the room” for the top lot price of $13,522,500 (est. $12-18 million).

De Pury didn’t announce the winner — as is custom and also required by the New York City Consumer Affairs Agency that supposedly monitors the auction business here — leading to speculation that it might have sold to Helly Nahmad, who was mostly invisible in a sky box above the salesroom. (Uber-clients such as the Nahmad family and the Mugrabis never raise paddles — like British royalty, they are unfamiliar with carrying cash in hand.)

Another Warhol, the spiffy, serial Disaster “Nine Jackies,” another guaranteed lot, from 1964, all of them stamped “Estate of Andy Warhol” and not bearing the artist’s coveted signature, sold to a telephone bidder for $12,402,500 (est. $10-15 million). It last sold at auction at Sotheby’s New York in November 1995 for $398,500 to Los Angeles collector and art patron Eli Broad. Alberto Mugrabi was the underbidder at that long-ago sale, according to this reporter’s catalogue notes at the time.

Other blue-chip works also found new homes, as Alexander Calder’s “The Whiffletree,” a jaunty and early standing mobile from circa 1936, sold to the telephone for $4,002,500 (est. $3.5-5.5 million). It last sold at Sotheby’s New York in November 2007 for $1,609,000.

John Chamberlain’s chunky steel, “Ivory Joe” sculpture from 1974-77 sold for $542,500 (est. $600-800,000) to Los Angeles dealer Patricia Marshall who bought it on behalf of Eugenio Lopez of Mexico’s Jumex Collection. It last sold at Sotheby's New York in May 1999 for just $40,250.

“The sale was very strong for the obvious things,” said Marshall as she departed the salesroom. “It’s a bit easier buying here.”

It wasn’t so easy, however, for Milan dealer Nicolo Cardi, who struck out in his efforts to buy works tonight. “It was a bad night for me,” said Cardi, moments after the sale ended, “I was the underbidder on four works [the Sterling Ruby, Elaine Sturtevant, the Rashid Johnson and the Richard Prince]. The market is very strong for quality works.”

Michael McGinnis weighed in on the results, noting, “There was a lot of art sold this week and I think we tipped over the billion-dollar market with this sale tonight. We’re happy with the results.” McGinnis acknowledged that the third-party guarantees came “from multiple parties” — a formula that has proved successful for this current era of risk-averse sellers.

Prices here include the buyer's premium tacked onto the hammer price: 25 percent up to and including $50,000; 20 percent up to and including $1 million; and 12 percent above $1 million.