Can someone with more experience on nickel coins tell me whether this is a proof coin? In hand, the fields are much more shiny than on the pictures. However the stars to the left are weakly struck and I thought proof coins are struck multiple times...?
I will say with 85% assurance that this is a business strike coin. The rims look rounded, not sharp and squared.
It is a business strike. Although there are a few dates that are known with incomplete stars on the obverse, it is quite unusual to find them on the 1900. Secondly, the reverse is ever so slightly off centered, that is a diagnostic that you should never find on proofs.
I checked with my ANA grading guide which clearly says where to look at, but I don't see any wear or abrasion. Where do you see abrasions?
PS: you could be right with regards to the cleaning... I am still unsure though, will need to look at the coin again by daylight.
It will be hard to see a trace amount of wear on a coin once it has been cleaned likt that. Generally though, you can hold the coin at a slight angle to spot the breaks in luster.
The locations of those hairlines indicate they are not die polish lines, to me at least. If they were die polish lines, I would expect to see at least a few going right into the devices and out the other side of said devices. Also, I see the same lines on top of the face and other devices. Not to mention they are huge compared to die polish lines. Quick example of some die polish lines.
I see what you are saying, but I would expect some frostyness around the devices similar to the OPs first coin if it were caused by cleaning. Hard to tell, but it doesn't have the look of a coin that would have been so harshly cleaned to leave marks like that.
To me, it also appears to not have luster either. That is another reason I drew that conclusion. Here are some full shots. I contrasted one to see if cartwheel is noticeable. It;s not.