Scored some Ampex but they might be junk...

[zenith2134]

I went into my local thrift shop looking for tape machines, vintage hifi gear, and vintage TVs. I usually go in there once a week. Well today I uncovered 3 never-opened Ampex 670 '90 minute audio recording cassettes' for a quarter a piece. They say, Redwood City, CA. Are these anything special or just yesterday's trash? I've yet to try one out.

[Scorpion8]

I know that 672 is Ampex's Cr02 formulation, and were well regarded tapes. But does it give a bias or equalization spec? My guess is they'd be Type I tapes, perfectly suitable for use but not the best available (even during their hey-day).