Definition of "unobserving"

It was full of heartbreak, and Katy was too unobserving to notice how round and steady and commercial the penmanship was, and how large and fine were the flourishes.

1888, Edward Eggleston, The Mystery of Metropolisville‎

In the old days, to my commonplace and unobserving mind, he gave no evidences of genius whatsoever. He never read me any of his manuscripts, […], and therefore my lack of detection of his promise may in some degree be pardoned.

1897 December (indicated as 1898), Winston Churchill, chapter I, in The Celebrity: An Episode, New York, N.Y.: The Macmillan Company; London: Macmillan & Co., Ltd.

Then she looked at Chase and winked, with a meaning nod at the unobserving Deppingham.

1908, George Barr McCutcheon, The Man From Brodney's‎