Is there anyone left to contact at Mitchell A Cotter about one of their SUT's?

I'm considering buying one of the Cotter Mk 2 step-up transformers used.  There is a lot of great information on this site and other sites about those units, their history and benefits, the different models that were made (P, S, L, etc.), their specifications and also how to reconfigure units to change their specification. 

But the particular unit I'm looking at isn't one that you can open the back to re-configure, which, from what I can tell from the owners manual online, means it was pre-configured at the factory as either an "L" (which would be perfect for me) or an "X" (which could be anything a customer requested as far as impedance matching).  The owner doesn't know which configuration it is, but does have the serial number on the unit.

Does anyone know if there is anyone left to contact in the world (I know Cotter has been out of business for a long time) to ask if they can tell from the serial number what specifications the SUT unit would have had when it was manufactured?  Or other ideas on how to determine that information from the unit?

Thanks in advance for any help.