The Alma listed by Willem Van Herreweghe Nurseries is described in their catalogue as HT, almost blue. It sounds unlikely to be the Riethmuller rose (Orange Triumph x Eutin).
1995 The Australian Rose Breeder’s Assn newsletter “The Rose Breeder”Vol 4-4. p18. Alma. Floribunda. 1957. F. L. Riethmuller. (Parentage: Orange Triumph x Eutin)