We want a sector of an annulus (ring).
* * *..
* |:::::* 405
* *:: 390 :*
* | *:::::
* * |@ *::::*
* * *----*----*
* *- r * 85 *
* * *
* * *
The radius of the smaller circle is
The sector has central angle
The arc length on the smaller circle is 390 mm.
The radius of the larger circle is
The arc length on the lartger circle is 405 mm.
Arc length formula: . . with in radians.
Smaller circle: . .
Larger circle: . .
Substitute  into : .
And we have: .
Substitute into : .
Construct two concentric circles with radii 2210 mm and 2295 mm.
Cut out a sector with central angle of radians or about 10.1 degrees.
The label is the curved region between the two circles.