I think you have the right birth date, Kath.
WWI Draft Registration Card
Gordon Armstrong
R2, Fremont, Michigan
born 23 Jan 1885
White, alien declarant, British
occupation - farming, employed by self
nearest relative - Weltha Armstrong, same address
Medium height & build, brown hair & eyes.
Gordon & Weltha's marriage record is here:
http://labs.familysearch.org/ She is transcribed as "Welthy".
According to the Michigan Death Index, Weltha Armstrong died 21 Oct 1972 at Sherman, Newaygo, Michigan. Her residence was Dayton, Newaygo, Michigan.