A most likely dumb question...

Okay.. on the old Vivitar 272 flash from the 1970's that used a pair of 9 volt alkalines-does anybody know if it was running off 9 volts-IE: the batteries were in parallel or 18 volts-IE: the batteries were wired in series like in flashes that use 2-4 AA batteries.

If they are in parallel, then logically you can find out by putting in just one fresh battery. If it works, then they are in parallel.