Philip Gosling, one of the four “founders” of the Bruce Trail, marked the first blazes marks in July 1962. The use of markers in the Bruce trail system dates back to that time.
The plaque is on the trail just north of Cambellville Rd (near Appleby Line by Philip. Just north of the plaque at the 1 km mark, there is the start of the Philip Gosling Side Trail, leading to Hilton Falls Conservation Area.
If you see no rectangular white or blue blaze, that trail is not part of the Bruce Trail system.