+1 - Very hard - mine took forever to lap with SGDLP - but once it's flat it will stay that way...
-john
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Here is mine, gotten over a year or more ago, and I lapped it immediately. As you see, the corner is still not lapped. At the first go round I called it 'good' when I knew I had enough real estate to hone a razor. Figuring as time went on I'd eventually get through that corner with the lapping plate.
Many, many sessions of lapping/honing later, it is what it is. If I live long enough maybe the whole thing will be uniformly flat one day, but no sense wasting stone, when there is enough to use, just to say "it's flat" ........ :)
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