Look at coupons. It is being used for bond coupons, shopping coupons, and vouchers. We should probably make some new tags. I suggest:
I wouldn't use "product" as discount coupons are as likely to be store as manufacturer.
a document exchanged in a retail context to provide a discount on goods or services
bond-coupon is fine.
I would, however, at least consider the option of leaving coupons covering discount coupons, and creating bond-coupons, and using tag usage guidelines. I feel like it's much more likely someone asking a discount coupon tag will not know to look at tag guidance than bond coupons.