It varies by manufacturer.

Storm and, I think, Roto-Grip, sand the ball to 600 or 800 and then use Storm's Step 2 to get to their "1500 grit polished".
(Personally, for Storm-made balls, I sand to 600 - 1000 grit and then use Storm's Xtra Shine.)

Columbia (AMF, & DT) has been finishing their resin pearls for quite a while now to 2000 grit polished. Most times they sand to 600 grit and use their Degree 2000 grit polish.

Legends uses a complex process whose last steps are an 800 grit nylon pad followed by their Legends factory finish polish.

Brunswick made balls usually sand their to 400 grit and then follow with their High Gloss polish.

Track has a different sanding for each ball, followed by their Magic SHine. (Carl, userid: C-G ProShop-Carl, has a list of several of their recent finishes.)
 
Lane#1's finish depends on whether Brunswick or Columbia made the ball.

Ebonite-made pearls do vary a little biut, but will often use 1000 grit plus their Factory Finish polish. A few new ones like the Total NV, ANgular One and the One are sanded to 4000 grit followed by their Factory finish polish.

Visionary finishes their to 1500 grit polished; I usually use my Storm method. I'm not sure how Visionary does thiers in factory.

I could have made a minor mistake here and there, but that's the best I can remember at this point in time.
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"None are so blind as those who will not see."

Edited on 5/19/2007 4:49 PM