Yup, that's Harris' writing.
These great, thick heavy bowls are properly early and absolutely, utterly stunning pieces. They don't seem to have become recognised for what they are, yet though. The big fuss about early stuff seemed to be mainly about Fish, Onions and Crizzle Stones, so much
other stuff got ignored, these bowls included.
I love them, they're so tactile as well as beautiful

Many of them do have lovely delicate "comet trail" features of silver deposits around them, a feature Harris was extremely good at producing, although Vicento Boffo and Said later learned, (although Said's were always a little bit less delicate.)
It was originally an accidental feature, but one that became deliberate.