In another forum I recieved an answer to my question.
The projectile is listed in HDv 119/419 Vorläufige Schußtafel für die 12,8 cm Kanone 81, 81/1, 81/2 und 12,8 cm Panzerjägerkanone 80 (L/55) mit der 12,8 cm Sprenggranate Flak 40 mit Rauchentwickler Nr. 9, 12,8 cm Sprenggranate 5151 (L/5,0) und 12,8 cm Panzergranate 43 (Ausgabe vom Nov. 1944, mit eingearbeiteten Deckblättern Nr. 1 - 9, Stand Feb. 1945)
the book "German artillery of WWII" by Ian Hogg gives some aditional information:
"12.8cm Sprgr 5151 L/5,0: fuzed AZ 23/28 or Dopp Z S/60, weight 28.00kg (61.74lb)
This  was the standard projectile that attained the maximum range. It is   believed that this was originaly a naval shell developed for the  12,8cm  SH C/30, since some specimens are painted yellow - a standard  naval  colour- had naval acceptance stampings and were dated December  1943,  before the K44 design was finished. Like Sprgr Flak 40 this  shellhad  double driving bands and two grooves behind the driving bands  indicating  that it had started life as a component of a fixed round."
I am now curious about fuzes used.
Bob