[Arran]

Daniel;
You are correct about your set being heavily modified, though the original set was also a series string set, here is the service info: https://philcoradio.com/library/download...l.%201.pdf I do not believe that it was intended for export, though I have heard that parts of Spain used to have 117-120 volt AC mains rather then the 230-240 they have today, so it's original owner may have been able to use it, as it was. Whoever modified it obviously wanted it to have long wave, or at least to have the band switch on the front, the original design had medium wave, and the old "Police Band" which covered what is now the upper part of the medium wave band. A few good points though, you still have the original speaker, knobs, and dial scales, and the cabinet is in good condition, apart from the extra hole.
It may be easiest to see if someone has a chassis for one of these sets, one that is mostly original, then to locate all of the original parts for this one. I think you are wise NOT to plug the set in, it looks like whoever modified it did so with the intent that it be operated from 117-120 volts like the original circuit, but replaced the old style American tubes with European Rimlocks, which were popular from the late 1940s through the mid 1950s. I have a British made Bush DAC-90A which likely uses the same tube/valve types as your set.
Regards
Arran