This extension should work on.... the 475, 476, 575, 577, 605, 610, 650 and 800.
Just to warn you, I only saw about 3% performance lift overall, although in some pure memory tests I saw about 14%. The CopyBits video tests also see reasonable gains.
This will not be any use if you are software overclocking your computer already and shouldn't be used at the same time as the 475 Overclock extension (fine with the control strip though). This should be most useful on 610s, 650s and 800s, although I have to admit I hoped for a bit more uplift.
Slightly unimpressive results from my LC 475 running at 25 MHz :
Usual caveats - what you do with your computer is your responsibility and not mine. While there is no reason why this should cause any harm to your computer (at all), if your computer stops working, please don't blame me! If you can't boot with the extension installed, hold shift to stop it loading and remove it from your Extensions folder.