Use available records
An accessible label, manual or previous invoice may provide a full reference. Include the unit's overall shape and connected fixtures if the label is hidden.
Avoid inferred compatibility
A similar appearance does not prove that a switch, seal or complete unit is interchangeable. The enquiry should remain provisional until the exact installed arrangement can be established.
A useful distinction
A manufacturer's family name may cover several versions with different intended connections. Include all readable suffixes and numbers, as a short brand name on its own may not support compatible parts identification.