HKS BOV - Genuine or fake?

I have received a 'HKS' Sequential BOV. It's the purpley bronzemodel but it feels really light and has casting marks which make me think that it's not the genuine article. In the outlet is says Sequential Blow Off Valve and there is a HKS label on the outside. The adjustment on the back has B on one side and A on the other. It's about 100mm long excluding the adjustment nut.

How can I tell a real one from a fake?