i recently found some old tin cans in the attic of my house. the cans once contained either corn or tomatoes and look like they are from somewhere in the 1800's. the cans have paper labels and one of them has a black slave woman holding ears of corn--the top of the cans have what looks to be a large flap that somehow sealed the cans. anyway-i can't seem to find any info on these. are they collectible?