With orders of $25 of more, Amazon offers Prime members the Stanley 8" x 12" Steel Carpenter's Square, model no. 45-912, for $2.99 with free shipping. That's tied with our March mention and about $5 less than you'd pay at a local hardware store. It features embossed graduations on face and back and a reverse reading scale.
Note that this item is sold as part of Amazon's "Add-on program" and can only be purchased with an order of $25 or more.