Never knew such a coupon code existed. You could do a simple google search to see if that yields anything. Otherwise you might have to turn to the secondary market for a set if you don't want to pay MSRP.
Well, I was browsing the website and noticed they offer coupons... Yes, I did do a search but nothing came up. http://sigmametalytics.com/purchase/cart.html I might buy of ebay, some seller accept offers.
You can buy off here: http://coppercave.com/copper/index.php?_a=viewCat&catId=50 $55 off rrp for the basic kit and $90 off rrp for the bullion kit. He ran the group buy at bullionstackers when these first came out.