Mercer binder
Holding page for this advert which relates to the "Mercer binder" for canvases rather than Mercer's treated fabric.
In 1904, a Frederick Duncan Mercer of 113 Haverstock Hill patented a method of tensioning belts/aprons used in reaping and harvesting machines; from the drawings included in the patents it seems likely that this was the same Mercer.[1]