Here are two Kodachrome samples scanned on my Epson flatbed.
The first was taken in 1941 with an early-1930s Agfa Memo half-frame [18x24] fixed-focus camera. I'm the young kid at the left end.
http://members.toast.net/rcarpen/family1941.jpg
The second [Silverton, Colorado] was taken in 1970 with a full-frame camera, maybe a Canon Pelix. Look at the clock on the County office building to get an idea of the resolution possible with a flat-bed scanner.
http://members.toast.net/rcarpen/silverton1970.jpg.
BTW, you may find that recent flatbeds will scan larger negatives (V500, etc.)