Both Windows, and Sandra read the cards BIOS, and report back what it says. All you have to do is to compare the video bios number to the known TI-4600 BIOS numbers from the same manufacturer and you'll know. Just going by the default core and RAM frequency is not always accurate, as some manufacturers have different default levels. It's even possible to set higher default levels in the cards BIOS with an editor, or flash a Ti-440 into a Ti-4600. The main difference between the two is the RAM. They share the same core in the newer revisions.
Either way, you can easily overclock the Ti-440 to way past stock Ti-4600 speeds.