I think the chance of getting them is more rare then the chance of getting donuts during the Halloween event. Which is odd. Halloween everyday I got 2-3 donuts from visiting friends or in my town. Somedays I got even four donuts a day but regardless of how many, everyday I got 1 or more. But since the update on Tuesday I got a total of 3 free coins from from gift boxes excluding the Eggnog coins, which would bring me up to I think I have 6 prizes now without spending donuts. But Thursday and today I have had town full of gifts but not one coin either yesterday or today. So hearing from numeruous people not getting coins I might have got lucky Tuesday and Wednesday by gettin 3 free ones within two days but the next two days I get nothing. But who knows its only 4-5 days into the update. Things might change.