Photography

Hi all. I apologized if this has already been asked. I didn't find any recent discussion on the topic.

I just collected around 2000 slides taken between 1970 and 1988, most of them Kodachrome.

While sorting through them, I used the date stamped on the slide carrier to organize them, assuming it was the date the film was processed. Generally, that seemed accurate, and aligned with my own memories and notes on the boxes.

One batch had me puzzled however. They are 110-format slides, and the date embossed (not stamped in ink) is about three years before the photo was taken (slide says Aug 75, but the picture was taken at a house we moved into in 1978)

Was my original assumption (date of processing) wrong?

The only possible explanation I can imagine is the lab used the date of manufacture on the roll. I'm hoping to find an answer to this, as this is a family archive, and I want the dates to be correct as I scan them.

Any help is appreciated, thanks!