In the mid-1920s, a news article mentioned that a couple of people from this firm had "invented a combination mitre jack and coping machine" and it was "coming into general use". The two people were Frank Acteson and William Greenfield. By 1927, Acteson had left the company and was president of a door and trim manufacturer. In 1928, a patent was awarded to William Greenfield for a "Miter jack and coping cutter". An example has surfaced that matches the patent drawing and is labeled, "GREENFIELD / PAT APPLIED FOR / SEATTLE". Based on all of this evidence, it seems that Tregoning was manufacturing this machine, or perhaps a predecessor to it, in the mid-1920s, although it is possible that Greenfield then struck out on his own and manufactured it himself, as neither the patent nor the surviving machine mention Tregoning.

Information Sources

• Thanks to Mike Kunnen for posting pictures of his miter trimmer, which was the first we had seen of this maker.
• A 1924-ish issue of The Timberman had this news item:

  Frank Acteson and William Greenfield, of Tregoning Manufacturing Co., Seattle, have invented a combination mitre jack and coping machine, which is coming into general use...

• A 1927 issue of American Lumberman mentions that Frank E. Acteson, formerly president and sales manager of Tregoning Manufacturing Co., Seattle, was now president of the Hardwood Door & Trim Co.