Heck, a ring would probably be one of the easiest "collars" to hide for my guy and I (especially one with an engravable inside). I have a friend who has gotten a ring from her boyfriend as just a present, and they never thought about it otherwise. It may be awkward if the ring has a diamond I guess... But meh. Jewelry is jewelry, hopefully you both feel that a ring should be an engagement ring when the time is right, and any other time a ring is just a nice piece of jewelry.