I'd bet AJ saw the one recognizable feature...some frills on a lady's skirt...and went for 1870s.
As for the rest of them, they are literally the size of postage stamps and no detail is visible. The first and third ones are completely glared out. We need to see a full-sized scan of every one. Tell your cousin they won't be damaged by sliding them out of the page frames, and any photo that isn't a tintype we'd like to see the back as well.
I'd say it would be worth the effort because tintypes were often done by itinerant photographers without fancy studios and props, and the results can be a charming slice of social history

Cheers,
China