Admission of additional evidence before appeals limited by exceptions, requiring written reasons and opportunity for examination and rebuttal. Admission of additional evidence before the Commissioner (Appeals) is restricted to specified exceptions (improper exclusion by the adjudicating authority; sufficient cause for prior non-production; relevance to grounds of appeal; denial of opportunity to adduce evidence), and any admission requires the Commissioner to record written reasons and to afford the adjudicating authority a reasonable opportunity to examine, cross examine or produce rebuttal evidence.