A few things have dawned on me since the last posting. The first being that Kate may well be Gladys Click Duff's auntie-in-law. Which would explain why she is situated in Scotland in both this card and the earlier picture. Of course she could have merely been on vacation in both instances.
Another clue that she might be Scottish is her use of "Yours aye." The term is a Scottish phrase used in closing letters which means yours ever or always.
As for the card itself it seems to be generic Scottish plagiarized from several sources including Auld Lang Syne. It looks like a good luck kind of horshoe wreathe which I would investigate if I was interested in that sort of thing.
Geographically speaking this card was sent from Biggar which is about 30 miles southwest of Edinburgh and West Linton is about the half way point between the two. James Graham Duff's hometwon of St. Andrews is about 50 miles to the northeast of Biggar and 50 miles east of Glasgow.
The Duff's address at 211 Grove Avenue in Highland Park, Michigan is the first mention I've seen of it but both James and Gladys died in that same city according to Find A Grave.
I also found an obituary for James:
The New York Times, March 11, 1941
Which led me to back to the snippet from The Numismatist, Volume 54, 1941 that was the source for the earlier posted biographical information. Adding Ford Motor into the search box resulted in finding a second portion of the death notice that I didn't know existed. The entire write-up follows:
Mr. Needles drafted a resolution honoring our late member, James Graham Duff. A copy is to be sent to Mrs. Duff and the A. M. A.
"James Graham Duff was born in St. Andrews, Scotland in 1872. In 1901, he was decorated by order of British Parliament for organizing the Tyneside Scottish Volunteer Corps. A student of philosophy and astronomy, he studied the fundamental principals at Madras College, St. Andrews, Scotland.
"He came to this country, and settled in Detroit in 1906. He was employed by the Ford Motor Company for twenty-three years in the metallurgy laboratories.
"He was an authority on Scotch and English coins, but preferred United States proofs. For years he had been a member of the American Numismatic Association and the Detroit Coin Club. He always enjoyed attending the local meetings, and had several articles published in The Numismatist and other periodicals.
"He is survived by his wife, Gladys Duff. He was buried in Acacia Park Cemetery, the services being conducted by Lodge No. 489 F. A. & M."