Interestingly - On a London, England, School Admissions and Discharges, 1840-1911 for Selina Maud Pember on 4 July 1904 it gives a partial date of birth as 31 March.

The SSDI shows - Helen Beck - Birth Date 31 Mar 1899 - 7 January 1988

(same person

)
Last Residence: 85351, Sun City, Maricopa, Arizona;
Issued New York before 1951.
U.S., Social Security Applications and Claims Index, 1936-2007 Helen Beck - Birth Date 31 Mar 1899 - Death Date 7 Jan 1988
Claim Date 1 Jul 1966
Sandra