"Protect your privacy with this handy device, easy to attach to doorknob or garden gate."
-- classified advertisement in the Daily Prophet (DP2)
Magical device that acts as an alarm when touched by a non-magical hand (DP2)
Offered for sale at 3 sickles each or 10 for a galleon and as an inducement to buy the December issue of Transfiguration Today magazine (DP2)
While the date printed on DP2 is 8 February 1999, the timeframe for these events is 1992-1993.