New York (CNN) -- Given the pedigree of 740 Park Avenue's past and present residents -- John D. Rockefeller Jr., philanthropist Irene Guggenheim, designer Vera Wang and businessman David Koch, to name a few -- it's no surprise the jewelry taken in several thefts since May is primo stuff:
-- His and hers Patek Philippe watches, a Rolex watch and diamond earrings and a diamond necklace (more than $100,000 total)
-- Diamond bracelet and rhinestone pin ($82,400)
-- Two diamond earrings and other jewelry ($53,000)
-- A $7,500 wrist watch
New York City Police are investigating grand larceny robberies at the most exclusive of Manhattan addresses. There were no signs of forced entry, according to Sgt. Carlos Nieves.
The building's real estate firm, Brown Harris Stevens, also is investigating, said Amy Gotzler, senior vice president of communications.
Police are focusing on four robberies that occurred while residents were on vacation, between May 30 and July 30.
Completed in 1930, 740 Park Avenue also was home to the parents of Jacqueline Kennedy Onassis. Current residents include business magnate Steve Schwarzman.
Some of its 31 units have sold for as much as $29.9 million, according to Michael Gross, author of "740 Park," billed as the inside story of New York's richest, most prestigious cooperative apartment building.
"In the last 30 years, it has developed a reputation as one of the strictest, hardest to get into, most exclusive," Gross told CNN on Thursday. "740 Park means that you're there. You're it."
Retired jewel thief Walter Shaw, author of "A License to Steal," said he believes the thefts are an inside job.
"Because if they go back to the surveillance tapes and cameras, they're gonna see that they don't recognize anybody that doesn't belong there," said Shaw.
Shaw was in the business for 30 years and is said to have netted $70 million in goods with his crew, dubbed the "Dinner Set Crew" because it robbed folks while they ate in a different part of the house.
He served nearly 12 years and was released in 1986 and later produced movies. According to Shaw, he and his team never did "high-rise" jobs because there was only one way in -- and one way out.
"I would think it's somebody that knows the building pretty well and knows the shift changes and knows the comings and goings of the maid service or construction being done, and they blended in," said Shaw.
Gross speculates that whoever robbed the apartments did so by locating each individual apartment's key box.
"Now you've got four unrelated families all during summer vacation -- when no one's around -- (and) someone managed to get in with no signs of break-in. Hello? That means keys. Where are the keys? They're in the key box."
CNN's Vivienne Foley contributed to this report.