Unusual US Cover To France

I saw an unusual US cover to France, anybody has an opinion?

The stamps aren't canceled?

I suspect that the stamps are not original to the cover and were added later; they seem much to fresh for the condition of the rest of the cover.

Yes, I think those 3 were added.

Correct. Stamps did not originate on this cover.

It's a stampless cover that was sent without prepayment. The NY Exchange office marking is in black as opposed to red as you'd see on a prepaid cover. It's also missing the boxed "PD" (Paid to Destination) that you'd see on a prepaid cover to France from this period. The "16" indicates 16 decides due from the recipient.

It is possible that there may have been insufficient postage on the cover at one point; the US-French convention did not recognize part payments so an insufficiently franked cover would have also been treated as totally unpaid.

Makes you wonder why someone do that to those beautiful mint stamps?!

There is an area under the 3c where a 1c could have been?
I can just see the gum remainder.
Strangely the address script appears to overlap the black Jack but be under some of the other stamps e.g. 3c.