By Daniel Eran Dilger

Published: 05:00 PM EST (02:00 PM PST)

Apple guided revenue for the September quarter 6 percent above consensus estimates, the highest differential over the Street in 17 years. However, that figure may still be conservative given current sales of Macs, new data shows.

In a research note to clients, Gene Munster of Piper Jaffray noted that Apple's guidance of $18 billion in revenue for the quarter "implies sequential growth of just 15% vs. 25% in the year-ago quarter," but in view of current Mac sales, the analyst said, "Apple's strong guidance may prove to be conservative."

Mac sales

The current quarter's Mac sales are tracking inline with Street consensus of 21 percent year over year growth, pointing toward sales of 3.7 million Macs. Munster cited NPD data showing domestic sales in July up 15 percent, and noted that international sales are growing even faster.

Early figures of the combined domestic and international growth in Mac sales point toward unit sales of 3.6 to 3.8 million Macs, representing growth of 18 to 24 percent, well above Apple's overall guidance of 15 percent growth.

iPod sales

Among iPod sales, NPD domestic data suggests unit sales of 9.5 to 10.5 million devices this quarter, in line with Street estimates of 10 million iPods. That range of sales suggested by early data indicates growth between -7 and +3 percent, compared to -1 percent a year ago and Street consensus of -2 percent growth compared to last year.

Munster wrote that new iPod products are expected in September, but that "it is difficult to gauge the impact these new models will have on sales late in the quarter.

"Additionally," the research note states, "international iPod sales are a larger mix than international Mac sales resulting in a slightly greater margin of error from domestic NPD data."

In the previous quarter, Apple noted growth of iPod touch sales up 48 percent year over year, despite overall flat sales for Apple's non-smartphone mobile devices in general.

"Killer" international growth

In its most recent quarterly earnings conference call, Apple chief operations officer Tim Cook stated, "The company's revenues in the Americas are growing over 40 percent, and so this is a huge number. It's not that we're talking about a low number, it's just that the international numbers are absolutely killer."

Cook cited growth of 144 percent in China, near double growth in Hong Kong and 71 percent growth in Mac unit sales in the Asia Pacific region in general. Revenues were up 160 percent due to new Mac sales.

Even in Spain, where the economy has been in the doldrums of recession, Cook noted 59% growth in Mac sales. Apple set a new record of 3.47 million Macs in the quarter ending in June, making Munster's current estimates of around 3.7 million Macs a new peak for the company.