def get_collection_no(row):
    """Get the collection number from an expedition row."""
    if row.get('collector_number'):
        return row.collector_number
    num = row.get('collector_number_numeric_only', '')
    verb = row.get('collector_number_verbatim', '')
    if verb and len(num) < 2:
        return row.collector_number_verbatim
    return row.collector_number_numeric_only