General ACCAShare Premium Account - Debit??

Hello people, This is just a general question. I am working on a set of accounts at the moment and there has been a debit figure on the balance sheet for share premium since pre 2005 year end, constantly b/f & c/f. (i.e. for at least 10 years!) It was my understanding that the share premium account cannot be a debit. Unfortunatly I dont have records going back further than 2005 so I cant follow it through. It isnt a material figure Im talking about, but Im just curious as to how it arose. I thought Share Premium accounts could only be a credit?? Any ideas?