From service document photo :
"30 AASS B.E.F 21-3-17"
From 'RE Library and Archive World War One Unit War Diaries' (Page 37 Section 138).
"30 Anti-Aircraft Searchlight Section 09 Mar 1917 to 21 Mar 1917"
https://www.re-museum.co.uk/wp-conte...iaries-WW1.pdf
So , perhaps if you contact the Royal Engineers Museum in Kent they will have more info.