Most likely it is U.S. Scott #65, which is the most common (and least expensive) stamp of that design. There are multiple other Scott numbers (64,65b,79,82,83,85,85C,88,and 94) of this design, but many of these stamps have grills, which can be seen on the back of the stamp, so it is hard to tell when they are affixed to a cover.
In an earlier attempt, a scan of the back of the pair showed pencil marks showing the grill at 12x16 which if correct puts the pair as #94 (F grill) which is also written on the back.
Take a good look at the cover. The stamp in the upper right corner appears to be the correct issue for the date on the cover which should place it as a US 64 or 65. That's my fault that I was not more clear as I was not referring to the bottom 3 (According to the date on the cover the other 3 do NOT belong on that cover and if you look at the cancels none of them are tied to that cover and they are all on top of the name and address) The best bet would be to find a way to remove those 3 stamps from the cover without trying to ruin the cover and leave the stamp in the upper right corner alone. It seems to me that if you are able to remove the 3 from the cover when they don't belong there it should make it easier to identify those 3 stamps.
Michael, as I said, in an earlier attempt at getting them identified the owner showed a picture of the reverse of the pair with said pencil markings. And you are correct as to the affixed stamp tied to the piece.
Comments
multiple other Scott numbers (64,65b,79,82,83,85,85C,88,and 94) of this design, but many of these stamps have grills, which can be seen on the back of the stamp, so it is hard to tell when they are affixed to a cover.
identify those 3 stamps.
I was just going by what he is showing in the 2 pictures above. (I didn't see his earlier posts) My fault. Sorry about that.