How Do I Tell If This Is Authentic?

This stamp is part of a collection I'm looking at buying. What should I look for to decide if this is not an altered stamp? Thanks!

Kelump, welcome to this forum! First you can scan this stamp and show us the backside as well. The photo needs to be sharper to tell anything - a scan would be preferred.

Peter

A backside scan would be revealing, but some things to look for in a genuine Scott #79, A grill: Points facing up when looking at the front of the stamp (seems to be the case here); points with rounded tips instead of horizontal or vertical ridges. In addition, genuine Scott #79's almost always have ragged-looking perforations (not unlike this example). A check of #79's offered by Siegel shows most have 26 or 27 vertical rows of points across the face of the stamp

Thanks guys! The stamp is in an album at the auction company. I can't scan it until I win the auction and bring it home. Looking at Siegel's helped, thank you for that suggestion. Hopefully I'll post a scan soon.

Kelump, please post your results. Good luck.

Curious to see what else is in that album!

Kelump-- Perfs are normal for an A grill, it is definitely "points up", the columns appear to be straight, and the shade is correct- dull rose.
Looks very similar to mine:


I can't imagine it not being a good 79....
Hope this helps, Ray

Thanks again everyone. The rest of the album is loaded with foreign stamps from 1840-1900. I don't know much about those so I'm basing my bidding on the 79. Would anyone be willing to offer an opinion on whether the postmark on this stamp affects it's value?
Without really knowing what I'm talking about yet, I think the centering is really nice but the postmark is heavy.

Here is one of the British stamps in the album.

The #79 in that condition is probably in the $300-$500US range.

Thank you!

Shame about the tear on the 1d black, as it has four margins - nice spacefiller, though.

The main issue in valuing this collection doesn't appear to be whether the stamps are altered, but how to discount it based on condition. For the 79, the owner was willing to tolerate a heavy double cancel, and staining. For the 1d black, the owner accepted he tear, a major fault. Most experienced collectors therefore would presume that there are condition issues with almost all the stamps, and discount accordingly, when there are too many stamps to evaluate individually.

So the album with the #79 sold for more than I was comfy bidding. Most of the U.S. stamps were in pretty rough condition and I didn't know enough about the other stamps to stay in the game. That album went for $850. There were some Confederate and Hawaii stamps as well as loads of early foreign stamps. I have some pictures if anyone wants to see them. On the bright side, I did win the second album (1900-1920 worldwide) offered by the estate. I'll add a picture to the "recently purchased" topic.