About 5 years ago, I played back a cornet tape I'd made in early '50s on a borrowed Webster-Chicago consumer grade machine (all there was for us proles, then.) .. played on a (much better quality) Uher Report-L portable of ~ late '60s vintage. WebCor brand tape - not even Scotch and surely before Mylar:
Eerily listenable quality (considering the toy mic and overall techno in the chain.)
Doesn't prove anything; likely an outlier. Much depends on how it was stored + the luck of the draw in that week's oxide slurry recipe, I'd suppose.
(Also best - store tapes in 'played' mode, not rewound; rewind to an MT reel to play. The echoes from print-through tend to be less disruptive musically.)
Gotta get this masterpiece onto later medium one of these years; the Uher is gone - a nice feeding frenzy on eBay for that little jewel; its numbers were ~Prof grade; quite better S/N, flutter than a Nagra du jour, etc.
Anyone have a medium-grade smaller (ie. not boat-anchor) R-to-R in the closet?