I don't know the equivalent (if there is one) for a PC keyboard.
Another thing I would do in this situation is power down, pull out the hard disks (all of them) from the backplane, and power up. This might just land you at the ok prompt. If it does we can discuss next steps.
(You mentioned earlier that "#." gave you ALOM login. To me this means that the boot process has progressed past the SC boot up and entered "autoboot" ie, looking at the hard disk. So let's pull out the disks to see if it gives an error like "can't access hard drive" and drops to "ok".)
Just an idea.