I missed your reply, thanks Bob!
You are correct, I don't see any advertising on this and the borders seem like a heavy paper/thick tape, so I think you might be right on with your thinking that this was a kit-produced piece instead of something made for professional distribution - something of a DIY MLS.
This image is known as a cabinet card:
https://www.nj.com/passaic-county/20...s-for-90k.html
I am not sure if there is any way to know whether that was produced from a glass negative or not.
Based on all of the good advice in this thread, this seems to be to most likely be a non-professional Magic Lantern Slide that wasn't produced in 1896 but is more likely from the height of Wagner's fame with the Pirates when someone would have wanted to show an old photo of him, so maybe ~1905-1915 would be reasonable.