Regardless of whether the bond has a coupon payment or not the face value of the bond is due at maturity. In your example the $1 coupon is still paid but in two

Regardless of whether the bond has a coupon payment or not the face value of the bond is due at maturity. In your example the $1 coupon is still paid but in two years you also get $100 back on your $50 purchase (netting 20+%apy). Of course if the government defaults on your bond you get maybe on $1 coupon and end with a net loss of $49.