Type 20 Other Ranks Badge.
This pattern of badge has sweat holes which would suggest a particular makers variation, in this case, the maker can be identified as Stratton of Birmingham. One large oval sweat hole (partially obscured by solder) can be found to the rear of the Coronet and 1 large and 2 smaller circular sweat holes to the rear of the Rose.
This example has a slider, it is believed this badge was produced around WW1 and would date it to between 1914 and 1919. Although maker marked badges are not unusual with the name being stamped into the slider facing to the back of the badge, this one is unusual in that the makers mark is on the inside of the slider and is facing to the front of the badge.