I have few lamps with different power. Example Primus 991, Optimus 300, Hasag 351L and Optimus 1551/500. So I can test various things. I also "know" few socks index value, because it is mentioned somewhere. Example sock pouch or selling description. I also have some reference socks from known manufacturer like Luxor or Auer. Well what I "investigate"? Example I have is Butterfly 500/600 CP socs. That one is 10cm wide when it is in it's packet. Then there is 8,5cm and 6,5cm versions. Those have quite big eyed net, so if I calculate 10x10/0,2 I can get value 500. That is pretty close what that sock can be. 8,5x8,5/0,2 makes ~361, what is pretty close 300/400 CP class 6,5x6,5/0,2 makes ~ 211, what is pretty close to 200 CP. When there is those "tubular" style socs, those are much smaller eyed net, so if I calculate example 6x8/0,16 (or 60x80/16) I get 300. That is close what sellers says of these socks. So, I have example 5x7cm socks, That makes ~219. 70x85/16 makes ~372 witch is 300 / 400 class etc. I'm not say that is the truth, but give a some point what lamp is potential test lamp when you get these socks or when you make your order... That is worked for me quite well by now. Otherwise those packs include usually much different sizes, so using that kind of calculation, you can forking a littlebit what you have =) That is not science, just fun and hobby.
