Hi there - I might have found some info on this, as I received this E-mail..
"This is a piece from the early 1970's by Robert Billyard. He was a local ceramist who did some of the frescos above the elevators in the Sturdy Stone building on 3rd Avenue. This is a signed piece... Dan from dansplace in Canada."It just so happens the place he refers to (building) are right here where I live....as I know the building he is referring to. So I will have to run downtown to check these out. That art on that building is local for me.
Not sure if Bull mark is his - but I might have to check this out more to confirm. And it might be worth more than I think it is worth....