This is a 1960 / 70's period tunic with older King's crown brass buttons.
Senior Aircraftsman patch to the left sleeve. There is evidence of a patch on the right sleeve but this has been removed. 
 
I have taken the following measurements as a guide for fit. Please account for under garments.
Arm pit to arm pit laid flat across the chest 19 1/2"
Waist laid flat 17"
Upper sleeve length taken from the seam of the shoulder to the cuff 25" 
Arm pit to cuff 17 1/2"
Drop centre back taken from the seam at the base of the collar to the bottom hem 29 1/2"
Shoulder to shoulder 17 1/2"
 
Condition: in good used condition. Some marks from wear. The label has been written on. 
 
Weight: 1.2 kg.