Yes, it is AT. Yes, it does decrease the value of the coin. Luckily, the coin was not worth much in the first place - it looks like a heavily dipped and AT'd AU common date coin, so its pretty much worth its silver value.
Feeble attempt to create rim toning by placing another object of a smaller diameter on both the obverse and reverse, before being chemically treated ...natural toning will not end abruptly as such, but will have a natural blending transition. Place a half dollar on the untoned area and see if it fits.
It does not appear natural. The tip-off, for me, is the abrupt nature of toned to untoned areas, and the extremely regular circular nature of the toning. Lastly, the lack of pull-back around the devices (date/stars/lettering on obverse) is a warning. At best it's secondary toned, at worst AT. All IMO...Mike
Not bad, lol. Way more than I'd ever pay for it... did you state that you weren't sure if the toning was AT or NT?