Its Scotch Broom, I've got a half dozen pieces but these are the largest.  Some of the others are less knotty but also much narrower; I may end up breaking these but learn enough of how the wood behaves to make a really good bow out of another pair of  SB billets - I haven't found that many completed SB bows out there, so I guess I'll be learning for everyone.  I'm thinking a three piece glue-up with a Turkish type handle and v-splices, slightly deflexed at the handle to keep the stresses on the wood low.  Not over worried at this stage, I have a plan b and plan c waiting in the wings.