With 'Press Studs' more likely for 'Warm Weather' No11 Mess Dress (White Jacket) than 'Temperate' No10 Mess Dress where they are normally stitched as are No1 Dress.
No3 'Warm Weather' is the equivalent to No1 Dress.
https://en.wikipedia.org/wiki/Unifor...monial_uniform
As Grumpy says for RQMS not CSM