K-line zinc pest

Does anyone know the approximate age of K-line sets that had the zinc disintegration problem. I like to pick up old stock but do not want to buy any disintegarting stuff.

Jim H

I bought a K-Line PRR B6s switcher about 3 years ago and have not had a problem. I would also like to know when K-Line was having this problem and what if anything they did to correct the problem.