Question About Folded Letters

Here are three folded letters I have without postal markings of any kind: no postmarks, ratings, or manuscript marks. They are from 1840, 1841, and 1850. I'm wondering if such covers passed through the mail this way or were simply never posted.

This is outside my realm and I don't collect US stamps or covers, but I'd like to know more about them before offering them for sale. Any input would be appreciated.

Often, as you may guess
correspondence was carried by friends aquaintances travelling
to mutual points of interest destinations, and mail was carried
free in the coat pocket.
Like members who use skips today, man is always alert to
a 'free" service.
This may be one explanation.

These letters were not carried by the U.S. post office or most private express companies. Although if was frowned on by their employers, many couriers did vest pocket deliveries for extra money.

So I guess you could call these 'surreptitious delivery' items. Thank you.

Offer them on the basis of local history and geanological value.

Hi Modern

Are there any other pertinent markings on the backs pf these folded letters? From your scans, I cannot see any postal markings on the fronts at all, unless my sight is playing tricks on me, and this wouldn't be the first time.

Nice pieces of history I would imagine.

Chimo

Bujutsu

Bujutsu, there are no postal markings on the back. One has a name and date.

Moonbird, my plan is to scan the letters and offer them as such to collectors.

Thanks.