Get Attribute with unkown classes:
SELECT
ea.attribute_code,
eet.entity_type_code,
ea.source_model
FROM eav_attribute AS ea JOIN eav_entity_type AS eet ON(eet.entity_type_id=ea.entity_type_id)
WHERE source_model IS NOT NULL
AND source_model NOT IN (
'core/design_source_design',
'catalog/category_attribute_source_sortby',
'catalog/category_attribute_source_mode',
'catalog/category_attribute_source_page',
'catalog/category_attribute_source_layout',
'catalog/product_attribute_source_countryofmanufacture',
'catalog/product_attribute_source_msrp_type_price',
'catalog/product_attribute_source_msrp_type_enabled',
'catalog/entity_product_attribute_design_options_container',
'catalog/product_attribute_source_layout',
'catalog/product_status',
'catalog/product_visibility',
'eav/entity_attribute_source_table',
'eav/entity_attribute_source_boolean',
'bundle/product_attribute_source_price_view',
'tax/class_source_product',
'customer/customer_attribute_source_group',
'customer/customer_attribute_source_store',
'customer/customer_attribute_source_website',
'customer/entity_address_attribute_source_country',
'customer/entity_address_attribute_source_region'
);