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OK, looking closely, I think I understand. The Sign is 3' x 2' x 1.5" at the edge, but thicker in the center - as opposed to being flat on the back, in the same plane as the rear edge of the steel banding.
You could use the grey (painted) steel - cutting it in two and drilling a hole the requisite distance from the angle to insure 'clearance at the rearance.' The original piece had two mounting holes and one 'suspending' hole. My grey steel has a single hole on (what would become) each leg. You would need to drill one 'suspending' hole on the one leg - ignoring the existing hole on that leg - and either use the existing 1/4" +/- hole on the other leg to fasten it to the wall, or drill a second hole in that leg.
As well, the little angles that 'came with' that grey steel thingamajig have the three holes like your original mounting bracket except, the 'suspending' hole is a slotted opening ideal for a carriage bolt. Using these would place the (center of the) 'suspending' hole 1 15/16" from the surface of whatever the two-hole leg was secured to. Since the original is 2.5" and the 'suspending' hole in it is 3/4" 'in,' could the center of the original 'suspending' hole be 2.5 - .75 = 1.75" from the mounting surface?
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