Can't Install OSX from Internet Recovery

I am trying to sell my iMac. I formatted the disk without problem & Disk Utility tells me the disk is OK.

But from the internet recovery I can't re-instal OSX at all.

Process:

After accepting T&C's I enter my apple id and invariably I receive the message "Item not available try later".

But Later does not change anything..

Note:

I don't remember which version my iMac came with (prior to Mavericks). I only ever upgraded to Yosemite. Recovery proposes to install Lion (I have no choice there).

Anyone with an idea is welcome :-)