Abstract: A changeable letter sign system including a plurality of panels, each bearing a letter, character or other suitable indicia and combinable on an overhead readerboard to display a message thereon, each of the panels having magnetically attractive material carried on the normally front face thereof, in complete contiguous arrangement with the peripheral inner and outer edges of the indicia on the panel, and including a tool having a magnet presenting a pair of feet for engagement with said magnetically attractive material to permit holding of the panels for placement on or removal from suitable retaining means on the wall of the readerboard.

Abstract: A security device (10) to releasably secure articles in a queue, row or stack has a body (11, 12) to be clamped on one of the articles by a loop section (14) and lugs (17). A key (26) attached by a chain or cable to a second device (10) is received in a slot (30, 31) in the body and is releasably engaged by a peg (39) on a pivotally mounted operating arm (34), in a cavity (29) of the body entering a slot (27) in the key (26). The key (26) can only be released when a coin or token is received in a coin holder (47) in a pusher unit (48) which advances a tongue (40), the nose (41) of which engages a cam face (42) on the operating arm (34) to move the latter to release the key (26). The pusher unit (48) can only be moved to recover the coin or token from the coin holder (47) when the key (26) has been reinserted in the body and engaged by the operating arm (34).