This technique was at the time the favorite of compact scale meth operations in the usa—combined with the misnamed “Nazi method,” which was commonest in agricultural spots with use of liquid ammonia fertilizer (Li/NH3 reduction or Birch reduction). These days small-scale operators prefer the one pot “shake and bake” approach, https://bluecrystalmath40011.digitollblog.com/29523533/blue-crystal-math-an-overview