Make & keep
Two dates for the same photo strip
Preserve both pieces of evidence and explain the disagreement.
A written year and a relative’s memory can disagree without either one being deliberately misleading.
Identify each source
Record the exact inscription and the person or document supplying the other date. Note whether either date describes the sitting, a gift, an album entry or an exhibition. Keep the date fields separate rather than picking the tidiest chronology before you know what each piece of evidence refers to.
Publish the uncertainty clearly
Use a description such as date uncertain with the two proposed dates and their sources. A range is helpful only when evidence supports it. Preserve your earlier notes if research changes the conclusion. Readers should be able to see why you dated the strip, not just encounter a confident-looking number.