"This is an on-going study and constantly changing article on the serpentine die cutting employed by Lowe-Martin to produce their coil stamps. Article updated September 12, 2016."

Robert Harris has been the editor of the Unitrade Specialized Catalogue of Canadian Stamps since November, 2004.

http://www.adminware.ca/LoweMartin/DieCutting-Sep12-2016.pdf

I find this article extremely informative and helpful when trying to identify the different variations of serpentine die cut Canadian coil stamps. Robert states in his article that "there are a total of 6,718 unique different specimens to collect (or ignore, depending on how smart or crazy you are!"