You might call around for a local PC repair shop to see if they have a memory tester you could use. Memory testers are expensive, especially the ones for newer memory like DDR. (example:
http://www.simmtester.com/page/shop/shop.asp)
also, see if there are any numbers or anthing that might allow you to identify the manufacturer
or
you could download Sisoft Sandra and benchmark the memory, compare the results with the listed memory types to see what kind you probably have
edit:
http://www.sisoftware.net/