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My vote is to use it. Frankly, it's not a work of art that will dramatically increase in value and earn you a significant amount of money. I would use it but would take very good care of it while making sure to properly preserve the paperwork and case that came with it. That way, you can still sell it down the road as a "near mint" razor and get close to top dollar.
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If it's one of the gold plated twist-to-open Gillettes, I might keep it cherry.
If it's a Super Speed, Fatboy, or Tech I'd use it. The old Gillettes are great shavers.