Newer black ones have had the spine labled on them for some time? I shoot mostly a Bob Lee recurve 64" 55@30 and I shoot the .340's.
I will say...I struggled for a while with GT arrow selection. I did the whole Stus calculator deal, other spine charts etc, but couldnt seem to dial it in. I got discouraged, but then I just stepped back and started from scratch.
I ordered a couple GT shafts in 3 different spines..55/75 and the 2 different spines of 75/95 (.340 and .300). I bare shafted each and really felt that .340 was where I needed to be, which was my original thinking. So I concluded that something else was wrong, and I was right. I took a hard look at my release. I found that I was torquing the string...a lot. I had sort of suspected this. I cleaned it up and my arrow flight immediatly improved to basicly shooting bullets.
Im actually glad I struggled with this, because I researched and learned a bunch about string release, which was quite interesting to me.
Anyways, sort of off topic, but hopefully my little experience will help someone out down the road, searching topics.
Mark
Edit to add...I always hate when Im struggling with arrow flight and I see others using the phrase "shooting bullets" lol....but..I had to do it.