- cellulose nitrate was first used for film bases but the problem was that they are highly flammable
- if caught on fire, difficult to extinguish, gives more oxygen to feed the fire and also toxic fumes
- aged and decomposed negatives especially flammable
- 1930s, replaced with cellulose acetate, with safety printed on the negative
- was an advertising point in '40s and '50s for old film boxes and the film itself being identified as safety film
- may include a date code (Kodak print films prior to 2001) or an actual printed 4-digit year.
- may include an emulsion number uniquely identifying the print stock (newer stocks, only)
- No Kodak film manufactured after 1951 is nitrate, and no film of any kind is polyester before 1955.
raw scan with no back light
assuming these were taken in 1953 as both had 53 on them
Self Scanned by: Canoscan 8800F
links/references
Photo.net - Kodak Safety Film
APUG - Kodak safety film
Wikipedia - Film base