Device Lock Error

Do they have a recovery partition?

yes, RecoveryHD

The EFI password is also set on all the Macs

I am getting this also. But I think the two laptop I am sending to are 10.8.4

This is always the Recovery HD partition image problem, I would briefly explain it.

How to get the reliable Image to use for Imaging many computers

- download latest OS X installer from Apple
- grab a test computer wipe it off and install the latest OS X you have downloaded (boot mac from a different drive or NetInstaller)
- after the latest OS X is installed on the test computer check the followin
- restart macbook and press Ctrl+R to boot the macbook from Recovery HD partition
- if all goes well then you pretty much have a reliable image to use for bulk imaging OR
- to avoid all above points grab an out of the box latest mac and use its image

NOW nuke and pave
- now setup admin password and basic settings
- connect the test mac to another macbook that has Composer and Admin installed in Target Mode which means you power on your mac by pressing T
- Now use Composer to make .dmg files of your test computer of both partitions i.e. Macintosh HD and Recovery HD
- Place both Macintosh and Recovery HD in Admin
- the point to be noted here is that both images must be from same macbook and same OS X to avoid such silly errors that initiated this thread
- Now add the Recovery hide script to Admin
- create the configurations in Admin (follow the Casper imaging guide)
- use Casper Image to image new macs

If the Ctrl+R is working on the newly imaged computers then Device Lock Error shouldn't turn up.

So I was actually over-confident and making images from different computers that caused this error.

@khurram, you can really cut down on the faff above & just use https://github.com/MagerValp/AutoDMG/
to create your OS.dmg.

Then as part of your Casper Imaging config set the admin password & settings. (For an example: https://macmule.com/2014/12/21/my-casper-imaging-workflow/)

Then when the next OS point release is out, just swap the OS.dmg... It'll save you time.

Thanks @bentoms
here comes something authentic, I would give it a go next time