Sheldon's site has Lambert info, and you might want to surf the web, too.
As I recall, Lambert's were sold as such for only a few years. Then Yamaha bought them and changed the name to Viscounts in (I want to say) '77. They didn't last much longer due to poor sales and the death fork thing. Maybe '83?
I knew better 3 years ago when I had a Lambert, but once I flipped it the knowledge slipped away.