You can test the LC with your K-2006. All you need is an eyedropper with a 1ml line marked on it--I'd get a glass one. They are still made and sold.

1) Test your tap water's FC
2) Add 10 liters of water to a 5 gallon bucket. I use an empty 2 liter Coke or Pepsi soda bottle and fill it 5 times.
3) Using your brandy-new eyedropper, add 1 ml of LC to the 10 liters.
4) Stir.
5) Measure your FC, and subtract the FC of the tap water.
6) The final FC is the concentration of the LC.

The dealer I like (the same one BigDave uses) sells LC that usually tests at 14% this way, though it's sold as 12.5%