Open System Profiler, copy your Mac's serial number from the Hardware Overview to the clipboard, then paste it into this form (opens in new tab) to find it out.

Older versions of OS X don't reveal the age of hardware so easily. Click the Apple icon in the menu bar, choose About This Mac, then press More Info. It's easy to confirm your Mac's age in Lion. Check out our list of OS X Mountain Lion-compatible Macs. Apple lists compatible models by the time and year they were introduced. Mountain Lion abandons support for some old models, some of which aren't really very old at all. If you're upgrading from Leopard or Snow Leopard, you'll need to ensure that your applications have been rewritten to support Intel processors. OS X no longer includes Rosetta, the technology that enabled PowerPC apps to run on Intel Macs. The maximum cost of upgrading your OS is £40, but check that any applications you depend upon have no known issues with Mountain Lion. Lion: If you’ve upgraded from Lion (or installed 10.8 onto a blank drive and imported your Lion data and settings), the first thing you’ll see when you log in to your account under Mountain. Snow Leopard is still available on DVD (opens in new tab) from the Apple Online Store for £26/$29. To get from Leopard to Mountain Lion, you'll first have to install Snow Leopard, because it's the earliest version of OS X with access to the Mac App Store. It installs an app named Install Mac OS X Lion. Safari downloads the following installer as a disk image named InstallMacOSX.dmg. Read our tutorial: How to install Mac memory To upgrade from Mac OS X Snow Leopard 10.6, download and install Mac OS X 10.6.8 Update Combo v1.1 followed by Mac OS X Lion 10.7.5.Most Macs provide easy access to their memory sockets, so you can upgrade much less expensively by purchasing third-party RAM and fitting it yourself, instead of paying Apple to do it. You'll need at least 2GB of RAM installed, but the ride will be smoother with 4GB. Some Macs that shipped with Leopard (10.5) are able to run Lion, too.

You don't have to upgrade to Lion first save some money and skip it entirely. If you're still running Snow Leopard, make sure it's updated to 10.6.8. You can upgrade straight to Mountain Lion from Lion or Snow Leopard.

Upgrade mac 10.6 8 to mountain lion