OK - the plot thickens...
Shot a roll at ISO 100 of several pieces of gray-to-black matboard & measured EV 7-11. Set camera at 9.4-ish (1/25 and f/5.6), then 1/10 and 1/5 and 1/2. First three frames made horrible noises while winding. Repeated same 4 exposures again (6x9 for 8 exp). Later found they were shredded.
Did roll at 7 minutes at buddy lab in Tmax developer (that's what they use).
Advise was 6 minutes and ISO 50 for next roll. No visible fog (not measured on densitometer) in my opinion.
Does 'nailing' the correct film manufacturer allow id'ing it's age better? Acetate more brittle than polyester?
Someone suggested 'flame test' to id acetate.
I'm just curious how old it is now that I see it's useable.