Help With Grill, Please!

Can you tell me what type of grill is bellow, please? Thank you very much in advance!
The image has the brightness decreased and the contrast increased because on the stamp the grill is very-very faint.

Might I suggest that the best replies come from supplying us the best initial information.

For grills, that would typically be:
1. a normally exposed scan of the front, to confirm design ID
2. a normally exposed scan of the back
3. an exaggerated contrast (or side-lighted photo) of the back to emphasize the grill.

Showing only a portion of a stamp can easily be taken as game-playing and decreases those willing to respond.

John Becker, sorry, I was too plugged-in: you're absolutely right
Here they are:






The light on the back of the stamp comes from the upper left corner, in diagonal, at an angle of around 30 to 40 degrees.

Soak the stamp to remove the paper hinge before scanning.

Cfrphoto, hopefully, I won't have to soak it:
after playing with the contrast, the brightness and the balance of black and white, to me it seems a 14x18 with horizontal ridges.
The grill ends below the hinge remnant.

You missed the point. No one can be sure about the condition of a used stamp if part of the back is hidden by a hinge or extraneous paper. Although, in this case, the condition couldn't be much worse unless the hinge is masking a deep thin or a hole in the stamp. In web terms, leaving hinges on the back of used stamps is like typing posts in UPPER CASE.

Aug-Stamps,
Listen, we all want all of our stamps to be world-class rarities. The special printings you've asked about in other posts never had a chance-- "special printings" were just that-- with wonderful impressions, and much whiter paper, and they were only sold to collectors who in the greatest majority of cases, didn't use them so not many are ever found used.

But on this one, I might be wrong but I'm guessing that you're hoping that you have a "Z" grill-- although you didn't mention that-- but you did say "horizontal ridges" which are only found on the elusive "Z" grills. The 10c "Z" grill is pretty rare-- rarer than any of the special printings, and IIRC, there are 2 certified copies in existence. Your ridges are not horizontal, and no way possible is it a "Z" grill.

Really, we've heard this a lot, and some other members have mentioned that you should always assume first that you have the least valuable variety of any stamp you're looking at, instead of assuming that you have the most valuable. If you start with the first assumption and read some of the reference material that is available online (I'd suggest that you go to uspcs.org, and start with the Brookman books on Classic US Stamps), you'll learn about the stamps a lot more, and you'll have a better chance of scoring when you actually find something that is better than ordinary.

Good luck with the hunt, Ray