1842 Liberty Seated Dollar

I also believe this coin is fake. I tried to attribute the die pairing and it looks like the OC-2 variety with the 2-A die pair. But the date is wrong. The upper serif on the 1 in the date is too thin. The lower serif of the 4 is too thin. And generally, the date is located too far away from the base of liberty.

Well this doesn't bode well for my first coin purchase in decades

No clue as to authenticity, but if real I'd say AU-50.

Here is the online attribution guide if you want to try to attribute for yourself:
http://www.seateddollarvarieties.co...ml#attribute

A quick way to determine authenticity with about 90% accuracy is to weigh it on a digital scale. A genuine coin should weigh 26.73g =/- .5g.

The counterfeiters are getting very close in their die creations, but they really don't want to put 90% silver in their planchets. Most counterfeits will be around 22~24g.

If it comes up underweight then you know it's a counterfeit. If it's within tolerances you would be advised to send it in to PCGS, NGC or ANACS for certification or confirmation it's counterfeit.

Upper reverse fields show signs of hairlines/cleaning. Not severe but still could cause a no-grade for cleaning.

This is considered a common date for the type and looks to be worth around $400 as-is.

I viewed the completed listing on ebay and my advice is to return it. I see signs of shill bidding and questionable listing practices. I believe it is likely genuine but could have problems as well and for what you paid? Top tier certified XF45 pieces are readily available.

When "newish" to collecting stick with certified pieces when dropping many hundreds of dollars on coins.

AU50. Although there looks like adjustment marks around the eagle's head. Not common a SLD so it may be scratches? Looks real to me.