Acronis True Image serial number confusion

I own 4 copies of Acronis True Image: one is V10, two are v11, and one is an upgrade to v11 from another v10 I owned and they are being used on 4 computers.

I'm re-installing one of these computers and am at a loss as to which of the 3 v11 serial# it's using?
I loaded the ATI-11 and went to help->about and there's no indication there.

Is there any way to determine which serial number is being used on the system before reinstalling so that I re-use the same serial number as before?

Thanks

Russell