OK, after doing some burn tests on pieces from edges of many pieces, I have more questions. If a piece of film is nearly 4 inches by 5 1/4 inches and has a hole/tear on one end (as if it had been attached on a spike or pin and then torn off), is that indicative of being pack film? These tend to be in groups of 1 or 2 good ones or 12 of similar timing. And when did that go from being nitrate to acetate (and there are several different types of acetate)? I can only find dates for Kodak and I am fairly sure my great-grandfather used others (at least Agfa-Ansco) at times. Almost no shots have edge codes or writing.
When doing burn tests, I'm taking a piece from the rebate that's about 2 inches long, holding it upright in kelly clamps and touching a match to the top. Some have obviously been nitrate as they burned right down fairly quickly. Some have fizzled out after 1/2 second. Others, curiously, have burned down a little ways then stopped. No real flame, and they look different when burning than the ones I'm sure are nitrate, but the test result is still sorta in between a positive and a negative. Literature I've seen states that only nitrate based film will burn down from the top. Oh to still have access to diphenylamine in sulfuric! I miss the lab (we used that stuff all the time). I'd much prefer to have two test results that agree.
[rant] Why, oh why, did he shoot with several different sizes of cameras and film? There will be an envelope that says "children 1922" and there will be 2 or 3 sizes of frames in that envelope. And no notation of whether they are his daughters or a mix of daughters and cousins. No envelope has a list of who besides the main subject is in any shots. [/rant]
Take a NEW piece of film and test that, learn how it burns, then compare, that way you have an example of guaranteed safety film.