Plain transparent cobalt blue tafl pieces from Birka grave 523 Hnefatafl or 'tafl' playing pieces, based on Viking-era gaming pieces from Birka grave 523 £4.00 Birka grave 523 had transparent blue glass beads with a black spiral and also plain cobalt blue pieces. The spiral pieces are available in a separate listing. The cobalt blue pieces measure approximately 19mm at the base but they will vary slightly as each one is handmade individually. The image shows the kingpiece from Grave 523 with the undecorated cobalt blue pieces. The price is per piece, the kingpiece is not included.