I'm not a Mac expert, but looks like an Apple Keyboard II, has Alps switch. I think you can use it on PC if you get an ADB to PS2 converter. They are on ebay for under $20 pretty regularly.
Top thing? Like you mean straight across? Was it an M0116?Show Image(http://upload.wikimedia.org/wikipedia/commons/9/9f/Apple_%28Standard%29_Keyboard_M0116.jpg)