Ohh congrats! Maybe HR4N refers to H & R nursery of Hawaii and 4N refers to its polyploidy (Number of chromosomes of a set)
Jeff, I think you gave me the clue I needed! Thank you! When I looked up H&R Nurseries, I could find the Dendrobium spectabile and saw several references to 'hr'. I believe you're correct that the 4N is the polyploidy.