Cliff - It seems the name is in fact xKalmiothamnus which would make the cross xKalmiopsis x Rhodothamnus. Barry Starling has already done the same cross a number of years ago and has named a plant in the past few years - xKalmiothamnus ornithoma 'Crinolines'. So xKalmiothamnus ornithoma 'Sindelburg'. If it's xKalmiathamnus then the cross was xKalmia x Rhodothamnus, I doubt this though.
john