Originally Posted by satwilson
Thanks for everyone's patience with me, it seemed a simple question, but I now realize it is a more involved assessment. Here is the link to Ebay which has numerous photos.
No Philips production codes are visible on these tubes, so unless they are hidden in the photos, I seriously doubt that they were manufactured in the Heerlen, Holland, factory. As others have pointed out, it is unfortunately quiet common to see "made in Holland" or "made in Germany" printed on tubes when in fact they were made elsewhere. (>_<). While I don't know for sure, it does seem quite plausible that they were manufactured in a Matsushta factory on an old Philips assembly line. Unfortunately, by 1974, as the state-of-the-art was transitioning from vacuum tubes to solid state, most vacuum tube production was retooled to meet minimum standards as cheaply as possible. Even so, as they were manufactured on Philips equipment, they may well sound quite good, but likely different than the earlier tubes manufactured in Heerlen.