[R] identical applied to data frames

[Rguy]

I have two data frames that I believe are identical, yet checking them with
identical() fails.

Each data frame has two columns named 'pk' and 'newv_f13__bool'. As shown
below, the columns of the data frames are identical, according to the
identical() function, yet the data frames themselves are not. How can this
be?

Browse[1]> identical(shft$pk, shft_mat$pk)
[1] TRUE
Browse[1]> identical(shft$newv_f13__bool, shft_mat$newv_f13__bool)
[1] TRUE
Browse[1]> identical(shft, shft_mat)
[1] FALSE

I have attached a file in which the two data frames are saved (using the
save() function).