Wicker baskets seem to have been used by the lexicographers as a handy way to store and transport individual bundles of slips that they were working on at any one time (as you can see in the photo of Craigie
here; click on the photo itself for an enlarged version). This basket was given its own photo; it presumably contains a selection of slips for the word 'what', a word that was eventually to occupy seven and a half pages in the printed
OED. The letter 'W' was a notoriously difficult one which consumed vast amounts of lexicographical time; it took several years to complete and far exceeded the 'scale' of treatment that the publishers had originally hoped for.
'Scale' had become a technical term used by the lexicographers and publishers to refer to the relationship between the
OED and the fourth unabridged edition, published in 1864, of
Webster's dictionary; the original hope had been to keep the new Oxford dictionary at a scale of six pages to
Webster's one but this was soon greatly exceeded. In 1924, for example, OUP's Assistant Secretary
Kenneth Sisam noted that the scale of
Well was 80 times that of Webster. In January 1926, as the Secretary
R. W. Chapman wrote to Craigie, they were still 'trying to give every ounce of energy to expediting W'; two months later they were still remarking on the letter's 'extraordinary difficulty' (
Brewer 2007b: 270 n. 45; for more on 'scale' see pp. 25-6).