By Jon Thompson

Published: 11:00 AM EST

Rumors that Apple Computer has been quietly developing its own spreadsheet solution gained a dab of credibility this week as sources pointed to a revealing company filing with the United States Patent and Trademark Office.

Just two days after requesting a trademark on the word 'Mactel,' which seemingly describes the convergence of Macintosh design with Intel hardware, Apple on June 8th filed for a standard character mark on the word 'Numbers.'

Described only vaguely by the filing as "computer software," Numbers may pertain to Apple's recently released graphing calculator application. However, the company in recent months has filed for other marks that more accurately describe that application, such as "Graphulator" and "Grapher" -- that latter of which is used in the shipping version.

Instead, Numbers appears to conform nicely to the naming scheme used by Apple to describe the components of its relatively new iWork productivity suite. Consisting of only two applications, the iWork bundle includes presentation software called 'Keynote' and a word processor dubbed 'Pages.'

After an initially modest start, iWork sales reportedly flat-lined by April, driving Apple to include a 30-day free trial of the software with each retail copy of its new Mac OS X 10.4 "Tiger" operating system. To date the company claims to have shipped over 2 million copies of Tiger.

Still, Mac users aren't adopting iWork in large numbers; partly because it lacks components like a spreadsheet application, but more so because Microsoft Office has established itself as an industry standard for home and office productivity.

According to sources close to Apple's retail operations, the average Apple store only sells a handful of iWork copies each week, if that. Meanwhile, contacts at larger mail-order catalogs have used words such as "awful" and "horrible" to describe sales of the software suite. Instead, sources say the first question to roll off the tongue of most prospective Mac buyers is: "Will Microsoft Office run on my new Mac?"

If Numbers does pertain to the rumored Apple spreadsheet application, is Apple hoping it will save iWork? A better question may be whether the company planned to include a spreadsheet application in the initial version of iWork, but somehow fell short.

According to the filing, the Numbers trademark carries a priority date of January 4th, 2005. This likely means that a division of Apple outside the United States filed for the mark a mere seven days before iWork was introduced at this year's Macworld Expo in San Francisco.

However, sources once close to Apple say development of the spreadsheet application began at the company's Pittsburgh, Penn.-based offices early this year -- the same location where both Keynote and Pages are rumored to have originated.

Sources, however, could not confirm an intended name for the application.