What's the serial number there on your secondary housing?
It's funny, but my new one has a serial number also on the secondary housing in the same place as yours, while my old one doesn't. It's serial number is stuck back on the tube where its meets the primary mirror case/housing.
Even weirder... the serial number of my original 9.25 is higher than the replacement, suggesting the replacement is older stock (earlier series number)
Weird.
Reckon I might have got one which had been on the shelf a while