Interesting use of the polarizing filter. Most people use the filter outdoors. It’s interesting to see an assignment that uses it in a macro indoor photograph.
Most interesting to me is that it seems to have corrected your white balance. The first image without the filter has an orange tint to it, while the second image with the filter seems to be more true to the colors of coins.
Many people notice this about polarizing filters. I was just doing a shoot indoors recently and the polarizing filter stripped a set of roses of their dramatic color so I needed to remove the filter.
As I’m sure you’re aware, the main use of the polarizing filter is outdoors where photographers use it to either take the reflection off of surfaces (such as water or windows) and make the saturation of the sky more vibrant and blue.
Also I made a reference to white balance above. This is a good opportunity to introduce you to color temperature and white balance.
There is a great lighting tutorial online that will help you understand how color is measured to ensure your images are properly white balanced. Please watch the short tutorial here:
http://www.youtube.com/watch?v=mwqNRqDx680&feature=channel_page
Thanks again for submitting this assignment. Great work.