It doesn't look like 139. It looks like one of the special printings. They are darker and richer in shade and color. These you can only ID by color shade. But...
Scott #139 can't have the secret mark and it doesn't. If it did have, it wouldn't be 139. If it is a 139, it will have the following characteristics...
H grill - 11-13 points wide by 14-16 points high (10mm X 12mm). If there is no grill, it can't be 139. This grill can be very hard to see. It is better to use a
strong magnifier and count the points if you can.
Printed on hard paper.
http://www.1847usa.com/BanknotePaperTypes.htmPerforated 12 (I think).
And use Stalzer's link explaining the shade lines.
If it isn't 139 then you have to get into the other varieties of this stamp and good luck with that. This can be a nightmare. You will have to have a current Scott specialized catalog and study it.
Not trying to pass the buck back to you, but the only one who can tell for sure on this one is the one who has the stamp.

-IBFS