how to read raw data from disk

I want to use LVM over LUKS. I just filled large disk with semi-random data: I've put LUKS on the new drive (with a password I have already forgotten) Then

dd if=/dev/zero of=<the whole encrypted PV>

Process has taken a long time... is almost ready... but now I am wondering if I made a mistake or not? So how do I check the disk to see if it is filled with zero's, or with random data?

Ideally I would like to grab a block of 1000-or-so bytes from a specific spot on the disk and see if it zero's or something else in there.

Thanks!

dd if=DISKDEVICE bs=1000 count=1 | hexdump -C

or more traditionally, replace hexdump with od