I have shared with my wife a desire for bondage and chastity play. but the vanilla is strong in this one. She has seen the cage both off and on (and didn’t seem freaked out) and while she has said she would try to indulge me it just hasn’t happened. Tomorrow she goes to work but I’m off, I’m considering putting it on and placing the key in her purse somewhere I know she’ll find it during the day. Im certain she would know what it is for. Think I may just go for it
You need to show her the benefits of you being cared. I was only able to convince my vanilla wife to keep the key to my cage after many months of treating her like a queen. She insists that I wear it now because she likes the attention. Maybe you could clean the house while you wear the cage, but I would wait on giving her the key. When she gets home show her a lot of attention without mentioning the cage. Hopefully she will ask and then you can go from there. It can be along process. Good luck.
Sorry to say but I'm afraid you're doing it wrong. Putting the key to her purse thinking that it will be a funny surprise for her is simple cheating or rather involving her in your kink without her consent. I do believe this must be HER DECISION to take, keep and manage the key. It seems that you did not make any significant effort to convince your wife to that.
Some really good advice above. It's so important for her to "want" to do this for her own benefit. That will take time and a lot of patience from you. See also this thread.......
And one more thing: in Nov 2018 you wrote that you talked a bit about cages with your wife, showed her two cages you've bought earlier, you've tried one of them and your wife kept the key for a few hours and... considering what you've written above - what has happened throughout last 3 years?