Provided labels do tend to be either used or discarded, hence rare, as in
Johnson’s Lives 1781. But in favour of Edward Pollack’s ingenious suggestion
is that the pre-1787 edition of Primrose Prettyface appears to be the only
book with such a note, whether with “withinside” or with “inside”: if a
publisher’s note, why should Marshall use it only for one book?
Further, the Pierpont Morgan listing states as present in their copy, in
addition to the note under discussion: "[Price six pence, bound, gilt, and
lettered.]" This seems to rule out a lettering piece for the purchaser to
paste on.
Against the Pollack suggestion is that the note appears to be dropped in
later editions, even when they are published by Marshall. Jokes are not
usually retired so quickly.
Sevin Seydi