This one is a bit rough indeed . . .
Go on eBay and do an advanced search of the completed listings. This will give you the most complete data available on recent sales. Then deduct for condition . . .
In good condition, it's worth about $350, but this one is not in good condition. Personally, if this were for a collection, I wouldn't pay more than $250, and $200 would be better. Your customer could then take it to a cue maker and have it cleaned up/repaired, and have a reasonable cue to display. This is not one of the more sought after models.
Good luck.