Can't Image our Macbook Pro

You cannot install an older OSX on a Mac than the one that it came with. You will have to accept that the new Macs will have to run Yosemite.

Ciao.

Here is an Apple support article in reference to your situation:

https://support.apple.com/en-us/HT201686

Remember that point about not knowing why you haven’t upgraded to 10.10? It’s probably time if you want to keep working with just one disk image. The new MBP computers cannot run 10.9. The rule of thumb is that a Mac cannot run an OS older than the one it shipped with. Although there are exceptions to this rule, in the case of the new MBPs there is no exception.

Having gone thru this dance many times with my labs, install 10.10 on one of your oldest and least powerful computers and see how it handles. I’ve found that 10.10 and 4GB of RAM don’t mix well unless the computer has an SSD. Upgrading to 8GB (or more) solves the problem. Right now I’m running one of my labs on two images: 10.10 for most but a few are stuck on 10.9 and I’m hoping they’ll be replaced before the new semester starts in the fall.

As I said, there are exceptions. Apple's hardware and software releases aren't perfectly timed so there are instances where a computer started shipping with one OS version, then the OS was upgraded and the computer then shipped with the new OS. Since the hardware was designed to work with the older OS, even though it shipped with the newer, it could be reverted and Apple would support that computer with that OS. The other exception is when a new computer model isn't substantially different from the older model and while you couldn't install the older OS on it, it could boot the older OS and run it. Apple wouldn't support this computer. The new MBP doesn't fall under either category since, among other things, the track pad is haptic which is brand new and not supported in 10.9