Rob was selling some of his pipes a few years back, so he put the information in his listings. Here's the rest,
"The second period (Mid 1970's to the mid to late 1980's) is the most famous period, as this is the era of Teddy Knudsen, Tonni Nielsen, and Former Nielsen, along with the occasional pipe crafted by Jess Chonowitsch, Peter Hedegaard, PH Vigen, and a few others. These pipes were stamped "Larsen Hand Made in Denmark" with no "Copenhagen" stamping. The staining of the bowls were more varied than the era before. The pipes crafted during this time began to show a more refined shaping, and the use of adornment materials expanded from lighter colored horn to now a darker color, bamboo, ivory, amber composite both for trim and stem work, and later in this period, some exotic hardwood for the trim, as Ole had explained to me that ivory was not as stable on airplane shipping and would sometimes arrive cracked. The pipes of this era are the most commonly found.
The third era was from the very late 1980's until the firm was sold in the late 1990's. The font stampings on the pipes is different - more modernized. Benni Jorgensen was the primary carver of the straight grain pipes at this time."