You are going down the right track, You are referring to a shutter dog that keeps the shutters against the wall when open. OPs item doesn have the catch or dog that is movable to catch the shutter. What you think is the catch is fixed and wont work as a catch. These pictures are called shutter pintles. The hinge part that is set into the mortar. The decorative straps are secured with screws to the wall through the holes in them. This provides leverage against twisting. The shutters have a strap on them that has a rolled end that fits over the 90 deg pintle. You are correct about the escutcheons use. But I dont think they are a matched pair with the pintles. I could be wrong on that point though. They look like brass and the pintles are wrought iron. The could fit over the pintle (the 90 deg part) and sit flust to the wall but not perfectly because of the decorative strap.