Type 17 Other Ranks Badge.
This pattern of badge has particular sweat holes which would suggest a particular makers variation (although the maker is not known). An oblong sweat hole can be found to the rear of the Coronet and 4 small circular sweat holes around a larger circular sweat hole to the rear of the Rose.
This example has a vertical shank (more commonly known as a slider). It is believed that this is one of the earliest York and Lancaster badge to be fitted with a short slider and would date it to between 1906 (when sliders started to become the normal method of fixing badges to headdress) and 1918 when this pattern of sweat holes went out of use.