I am not sure, but I think the cost is $20.00. They must remove the thumbstud to polish the blade, and I think they only polish the ground portion, not the flat. Take the opportunity to add an ambidextrous thumbstud while it is at the shop, always a nice option. Of course, you should contact the folks at CRK to confirm costs, times, and availability.
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James Segura
San Francisco, CA