Thorn 400w MB/U mercury lamp

I was very lucky to find one of these for a very reasonable price on Ebay, a seller had unknowingly listed some for bargain prices and within a few hours all the stock had been snapped up! I have yet to light this but I rather love the characteristic frosted arc tube that Thorn used to employ on their MB/U lamps. Was this to reduce glare? Sadly the etch on this lamp is smudged and virtually un-readable.