What are your thoughts on a "pre-engagement" ring?

My (29F) 34 year old boyfriend of 1.5 years recently told me he wants to give me a "pre-engagement" ring and wants me to wear it around everywhere to show everyone that I am "off the market". I don't know about other people but to me, it sounds a whole lot like a "promise ring" high school kids/teenagers give each other. He meant for it to be a sweet idea and gesture but I am actually quite offended. If you don't have the real deal to offer me, don't try to claim me and take me off the market for 1/8th of the price. He's 34, not 17. Am I wrong for feeling this way?
What are your thoughts on a "pre-engagement" ring?
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