BOSTON (Reuters) - Apple Inc unveiled its largest US store yesterday, a glass-facade building sheathed in steel that a senior company official said reflects Apple's plans to expand retail ventures at home and abroad.

Sandwiched between aging brick buildings, the minimalist 20,000-square-foot store stands out on Boston's historic Boylston Street, featuring a ground floor with more than 100 Mac laptops and computers, a second level for iPod music players and iPhones, and a third entirely for service.

Apple's second-largest store globally after London's Regent Street offers a vivid glimpse into the latest retail thinking at the Cupertino, California-based company as it prepares to expand internationally with a new store in Beijing this summer.

"Concierges" stand at attention in orange shirts bearing the slogan "I know people" — part of changes made in recent weeks to more thoroughly identify roles played by employees with the colour of their shirts worn in Apple stores.

A sales force of "specialists" wear aqua blue and technicians are each dubbed "genius" as they work the third floor wearing dark blue — all projecting a trademark retail image that has helped drive sales growth.

"These stores have served them very, very well and really raised the bar in terms of technology customer service," said Michael Gartenberg, an analyst at Jupiter Research, a technology consulting firm.

In its latest financial quarter to March 29, Apple's store sales leapt 74 percent in dollar terms to nearly $1.5 billion. Average revenue per store in the quarter reached $7.1 million, up 48 percent from a year earlier.