That is 2 1/8 for the facing. If hand sewing, the inside works itself out easy enough. Just line up the middle of the inner pleat the stitching. The back facing and the forward sections of the inner pleat become evident. (That's what I do.)
IF you want to measure it, it would be 2 1/8 for the back facing (what is toward you) and 1 1/16 on each side (for the part linking the front and back facings.

I'd also look at 3 1/4 for each facing, alternating centering between pivots (for a pivot-> I'll use Wallace-> one is the yellow on black and the other is the black on red). That is what I did for the USA and the MacNeil.