Well, if it was "glass bead" blasted, it will have to be cleaned out thouroughly to be sure to get all the blast-media out.If plastic beads or walnut shells were used, it is not so much of a big deal, but I would suggest cleaning it out ANYWAY!
If a person can get the inside clean enough, they can paint the inside to help seal the pores of the cast-iron metal. Doing so will help to hold any particle which may have been missed.

There is enough good in the worst of us and enough bad in the best of us that it does not behoove any of us to criticize the rest of us.
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Be yourself. If you are ever lost, It will be much easier to find yourself if you know who you are!