Only you can decide.
I suspect you already know the answer. Your reaction to the responses of others will likely serve to validate your perhaps unconscious thoughts. So here's my input.
It's a nice looking watch, aside from the circumstances of Hairy's death. If looking at it makes you remember Hairy, then that would be nice in the future when the pain has passed. Of course you will always remember Hairy and likely won't need a watch to prompt you.
The ying/yang of the dial seems appropriate as a memorial. You can't enjoy the love of another without knowing the presence of death and separation. Hopefully, the life of sharing will dominate the pain that is inevitable and will come. As in this dial, the red dominates the dark.
I like gold myself. It's one of the benefits of aging, as an older person can wear gold without seeming pretentious. If you aren't there yet, you'll grow into it.
Good luck with the decision. Hope this helps.
I also hope pictures of Hairy will still find their way into the forum. I suspect there will still be threads in the future that will need the calming distraction of a cat.