identical(coordinates)

Dear all,
I need to convert several times sp objects from data.frame and use
zerodist2() to match locations.
As zerodist2() seems to use identical(), something seems strange to me:

library(sp)

xy <- data.frame(x=rnorm(4), y=rnorm(4))
dfxy <- xy
coordinates(xy) <- ~ x + y
dfxy[1,1]
coordinates(xy)[1,1]

identical(dfxy[1,1], coordinates(xy)[1,1])

FALSE        # I should expect TRUE!?

coordinates(dfxy) <- ~ x + y
identical(coordinates(dfxy)[1,1], coordinates(xy)[1,1])

TRUE

Why identical(dfxy[1,1], coordinates(xy)[1,1]) gives FALSE?

all.equal(dfxy[1,1], coordinates(xy)[1,1])

(dfxy[1,1])

coordinates(xy)[1,1]

Thanks,
David

sessionInfo()
R version 2.14.1 (2011-12-22)
Platform: i386-pc-mingw32/i386 (32-bit)

locale:
[1] LC_COLLATE=French_France.1252  LC_CTYPE=French_France.1252   
LC_MONETARY=French_France.1252 LC_NUMERIC=C
[5] LC_TIME=French_France.1252

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
 [1] rgdal_0.7-5     trip_1.1-10     maptools_0.8-12 lattice_0.20-0 
foreign_0.8-48  rgeos_0.1-17    stringr_0.6
 [8] sp_0.9-93       spatstat_1.25-1 deldir_0.0-16   mgcv_1.7-12

loaded via a namespace (and not attached):
[1] grid_2.14.1  Matrix_1.0-2 nlme_3.1-102 plyr_1.7.1   tools_2.14.1