Yesterday, technology titan Apple (Nasdaq:AAPL) reached a total market capitalization of $620 billion as its stock hit a record $665 per share. The stock continues to trade up and recently surpassed $666 per share for a market cap of nearly $630 billion. Many headlines have since proclaimed that Apple has broken a record for the most valuable company ever. However, this may not be the case.

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Was PetroChina Bigger?
A perusal of headlines for the past record-breakers, in terms of the largest company ever, uncovered PetroChina's (NYSE:PTR) value after it went public in October 2007. PetroChina held its initial public offering in Shanghai back when sentiment on China's overall growth prospects were about as rosy as they could get. Offering the opportunity for a public investment in one of its largest oil companies and a true national champion was too tempting for many investors to pass up. As a result, media reports detailed that the stock doubled after it went public. A share price chart of the U.S.-listed ADRs confirms a steady rise in the share price, and a stock that hit more than $255 per share by the end of October. But by the time of the public offering, the state market cap had already exceeded $1 trillion, which is well above Apple's current public value.

SEE: What Is The Intrinsic Value Of A Stock?

Archrival ExxonMobil (NYSE:XOM) traded at nearly $500 billion at the time of PetroChina's IPO, but it was still dwarfed by PetroChina's strong initial run. The argument for Apple to maintain its status as the world's most valuable company may not be considering nearly 158 billion PetroChina shares that were considered inactive and held by Chinese state entities. But this would still technically be part of the share count to consider an overall market capitalization.

Microsoft in Today's Dollars
A couple of other media sources, including the "Columbia Journalism Review" and Standard & Poor's, have pointed out that Microsoft (Nasdaq:MSFT) was more valuable when adjusting for inflation and calculating its market cap in today's dollars. Back during the near peak of the dotcom bubble in 1999, Microsoft's stock was trading in the stratosphere and had a stated market capitalization of just over $620 billion. Adjusted for inflation, Columbia estimated that market cap at $850 billion. By this measure, Apple's stock would have to rise another 36% to above $900 per share to match Microsoft's inflation-adjusted level more than a decade ago.

SEE: Market Capitalization Defined

The Bottom Line
Apple may not technically qualify as the most valuable company ever in terms of market capitalization, but its valuation has reached all-time highs. This certainly qualifies it as one of the most valuable companies in history. The real question for investors is if they should buy, sell or hold at today's prices. For investors that have held the stock for some time, it could definitely make sense to be trimming positions right now. Holding may make sense for investors who are extremely optimistic about the prospects for the next version of the popular iPhone smart phone device.

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Other investors may simply seek to avoid the stock altogether. The company is certainly riding high with its iPhone and iPad tablet device, but the market for electronic gadgets is fast-moving and extremely competitive. Just a few years ago, Nokia (NYSE:NOK) dominated the mobile phone market with a global market share above 40%. These days, its fortunes have changed drastically and it holds only a single-digit share of the smart phone market. Motorola (NYSE:MSI) had a similar dominance in the mid-2000s, but it's a shadow of its former self. Apple will likely not have a similar fate, but further upside in the stock is by no means assured given the competitive dynamics of the business it operates in.

At the time of writing, Ryan C. Fuhrmann was long shares of Microsoft (since 2007) but did not own shares in any other company mentioned in this article.