I'm betting on 70s/80s vintage, and pretty much a Hitachi badged Trio-Kenwood, or vice versa.
I'm guessing a Japan manufacturer at that time putting badges on these oscilloscopes
IMHO, these storage jobs are hard to beat for audio purposes, and I much prefer them to DSOs
and 10 mhz is more than plenty bandwidth for audio, and more... and likely less trouble and HF noise to spoil the show
TBH I never understood the big deal with Tektronix scopes because I used these MIJ ones before going with Teks later,
yes the Teks are nice
but upon side by side comparisons in the 15 to 100mhz bandwidth bog standard models, pretty much the same.
The Tektronix storage scopes rock, but the Phillips equivalents were pretty good too
The MIJ scopes were a LOT easier to get into for servicing, and that's why I have a couple still kicking around.
Even if they are crusty, after a warm up and exercising the controls and switches, they work great and still in CAL
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@ OP Krusher: does the scope perform XY in strorage mode too?