How do I tell what type photo this is?
 

I've searched the blogs and wasn't able to find any definitive explanation of how to tell what type a photo is. I'm posting here. The back is blank, the front is glossy, the detail - even enlarged - is sharp. (I've also searched the internet for images and can't find a similar one.) Probably a dumb question, so please excuse me asking, but thanks for any input.

I know you said the back is blank, but might be a better clue if you could post a scan of the back. Possibly with the contrast scaled down a bit, if you know how to do that.

These types are often much harder to tell without having them in hand. Even in hand, a strict PSA type definition is usually just a guess.......or "in the ballpark", if you're looking for it to be a Type 1.

You're right. Had to play with it a lot, but the back says "this paper manufactured by Kodak." According to Cycleback's book, this back-printing was used in the 1970's-'90's. So looks like a Type 4. But still, perhaps, from the original negative?