Looking at the photo in that link I noticed the rockers still installed. The TSB on this indicates the castech casting logo can only be seen with the rockers removed. Here's a couple screenshots from the TSB.
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I am currently experiencing this very same condition, although I also do not have the bubbles that @Doubeleive has. I have pulled the covers and found a leak/crack...
That is true. Once I stripped the head of the rockers I was able to confirm there was no Castech logo.