The claimant or any other interested party may file an appeal from an initial determination, redetermination, or subsequent determination not later than ten days after the determination was mailed to his last known address, or otherwise delivered to him. The term "any other interested party" shall mean and include the claimant's last or separating employer, and any employer whose account may be affected by the adjudication of the claim. If an appeal is duly filed with respect to a matter other than the weekly benefit amount or maximum amount of benefits payable, and the appeal tribunal affirms a determination allowing benefits, such benefits paid prior to the decision disallowing benefits shall not be recovered from any claimant regardless of any appeal which may thereafter be taken to the extent that such benefits are not charged to the account of any employer.