Spine of Glashaft K75?

[TRG 1]

In rummaging through some old arrows, I came across a dozen black fiberglass-type marked "Glashaft K75". They are 28" in length. I shot a couple in my Firefly 53# longbow and the tail end seemed to flick back and forth more so than arrows I usually shoot in this bow even though they did straighten out and hit where I was looking. Does anyone know the spine of these arrows? Thanks, Tom

[Orion]

I have an old Gordon Glass Shaft chart.  Don't know if it's the same thing.  Regardless, it runs from A-20 through J-65.  No K-75. The J-65s are 67#@28.  Through extrapolation, I'd guess K-75s would be 10 pounds heavier.