Triumph motorcycle Engine coating help

[njpittfan]

Ok , Here is something that i have been trying to find out for years.What did Triumph motorcycles coat their aluminium engines with.Im really not sure if they are coated at all but it sure does look like they are.The finish isnt the same after you bead blast them wich leads me to believe they are coated with something.Hopefully there is a triumph nut out there like me who has this piece of info.Keeping my fingers crossed.Fred

[Popeye]

The older ones were clear laqured... tended to yellow and chip