Holset HT4B?

I'm having a hard time finding the the turbine housing size on my newly acquired Holset HT4B. I had a HT3B a few years ago and it was clearly marked with a 26 inside the volute. Well, my problem with this turbo is that all that is stamped in the inside is a single line. There are a few numbers on the outside, but nothing stands out to me. I found a thread on here in the for sale section and he stated his housing was marked the same; from what he gathered it was a rare 21cm single scroll housing. Link to thread below.



http://ift.tt/1AfTFCz