Abstract: An orifice fitting of an orifice meter installation is provided, in accordance with one embodiment of the invention, with a tamper indicating cover positioned in a manner to obstruct access to the bolts which clamp the seal bar into sealing engagement with the fitting housing. Because the path of orifice place movement into and out of the fiting extends through the position normally occupied by the sealing bar, the tampering indicator also spans the path of movement of the orifice plate. The tampering indicator is made of plastic material having an external surface of one color and an internal surface of contrasting color. To gain access to the clamping bolts and to move the orifice plate out of its seated or operative position, the tampering indicator must be destroyed. Destruction of the tampering indicator is visible from a substantial distance. In accordance with another embodiment of the invention, the tamper indicating cover is positioned to obstruct opening movement of the clamping and/or sealing bars.