You should be able to tell by looking at it -- aluminum can't be blued, so it won't match the rifle finish very well. If that fails you can always try sticking a magnet to it.
I will call Monday and request steel mount and base and see what I get. Did you request a steel base? Also, scope has 1959 stamped with refurb square.SOG in October 07. It is a 1943 Izhevsk that is in excellent condition. The rifle is very accurate with great optics and all steel mount and base. The gun would shoot better if the said shooter/operator was any good. Bob