The showy part of this mirror is the acanthus. The part that decides whether it looks right is the row of beads around the plate.
A beaded moulding is a repeating element, and a repeating element has to arrive at each corner cleanly. Run the beads at a standard pitch and you finish with a half bead in three corners out of four, which nobody can name but everybody notices. Our artisans set out each side separately, count the beads that will fit, and then adjust the pitch by a fraction of a millimetre across the whole run so a full bead lands exactly at each mitre.
Because the mirror is made to order in your dimensions, that count is redone from scratch for every single piece. The bead is not a stock moulding cut to length. It is set out for your frame, on your proportions, so that the tightest, most disciplined element in the design stays disciplined - and the acanthus around it is free to be as loose and unruly as it likes.