Wow, that one was once a really nice onionskin (german handmade). It would be a good candidate for polishing in my opinion, as it has little value in the condition it's in.
From what I've seen on ebay, polished marbles can still go for decent money if they are nicer ones. Some beginner collectors want certain marbles, but they can't afford hundreds for pristine marbles, so they buy the cheaper damaged and polished marbles. An advanced collector doesn't want polished marbles, but they don't want beat up ones either unless it's a very rare type or has some special interest about it. Polished marbles look new and display well but aren't worth near what the same marble in pristine condition would be worth. Do some reading online about the subject and figure out what you think about polishing. Some collectors are dead set against it, some are all for it when conditions warrant. Here's one I did: http://forum.treasurenet.com/index.php/topic,387473.msg2756380.html#msg2756380
Look at this marble forum, there is a member here that is easy to find while browsing the forums. His name is richsantaclaus. He remelts marbles, which is probably even a better option since it removes no glass and the marble diameter stays the same. He is VERY reasonable. http://www.allaboutmarbles.com/index.php?sid=6fe6b3220e105f56f13013d4b1d0430c