This button is from the era before the federal penitentiary staff uniforms were standardized in c.1896. 

British Columbia Penitentiary opened in New Westminster, B.C. in 1878 therefore the button cannot be older than that date. British Columbia Penitentiary was decommissioned in 1980.

Other similar examples from Kingston Penitentiary and Manitoba Penitentiary have been located.  It is assumed that Dorchester Penitentiary (a.k.a. the “Maritime Penitentiary”) and St. Vincent de Paul Penitentiary may have also used unique buttons during this period.  The back-mark of this example reads “Extra High Quality”.