The Monthly Army Lists for July and December 1921 show the 2nd Battalion SWB at Jhansi. Not sure that's helpful in that Jhansi isn't a place in the TNA Catalogue description of RG 15/28121, the 1921 census piece in question.
From the army birth returns, a 2nd Bn. South Wales Borderers birth.
Sybil Catherine born 13 Oct 1921, at British Station Hospital, Jhansi
Father Walter D Arcy (I think D'Arcy), who was a C.S.M., mother Sarah Ann (Lowe)
The Officer registering the birth was O.M. Wales, Capt. Adjt. 2nd S. W. Borderers.
Could Walter be the
Walter Daisy born 1895, Egypt, at Chaubattia in the 1921 free index?
I notice there is some poor transcribing of the less common surnames going on here.
Putting Company Sergeant Major in keyword search also brings Walter Daisy up.
Also using Chaubattia as a keyword we get Owen Murton Wales, born 1895, Pontypridd, Glamorganshire. Presumably that's the O M Wales on the cert.