that's brass allright..... you will notice it to be very easy to drill, and the shavings will not be so stringy... it will allmost form a corse powder as it comes of the bit.... Copper makes nice long curly loks that is very sharp. and a pain to get out of carpets....
Brass is an very good material for the top plate, if you want to polish the end product. It looks awesome when you put a little bit of effort into it. and it polishes much easier than copper....