An anti-tamper device in the form of a collar fitted about a housing is provided. The ends of the collar are formed into lock tabs, one of which is formed into a U-shaped portion, or V-shaped portion, to permit capture of the end of the other lock tab. Movement of the captured tab is prevented to resist tampering with the housing. Embodiment of the invention find application, in particular, to a housing for a bell at a railroad level crossing, and prevents loss of the bell due to vandalism.