You are well read on Manx coins, there is alsoa stand alone 5p coin ehich has a golf ball on the reverse, this was issued specially for the Coin News magazine to give away as a cover gift, and some do occasionally turn up in change.
Unfortunately every year we here in the Isle of Man release special 50p coins for Christmas, which only serve to bring more revenue to Tynwald. Mind you we produce so much dross over the course of a year that it is a wonder anyone takes Manx coins seriously.