What Are These Grooves On 1876 S Trade Dollar Type I/Ii? Please Help

I have very little experience with Trade dollars and was hoping someone could tell me what the grooved lines on this 1876-S example -- especially on the reverse -- are, and/or what they indicate. This coin has a Type I obverse and Type II reverse.

The uniformity and consistency are similar to die lines, as opposed to scratches/hairlines, but of course these are not die lines as they are incuse and run over the devices.

So ... Cleaned (I mean aside from the obvious obverse cleaned area)? Tooled? Whizzed? Counterfeit? Mint error? Something unique to Trade dollars?

I took a chance on this one on ebay from a seller who I've bought from -- and returned to on occasion -- before so I'm not worried about being out any money. It was described as "BU" but wasn't expecting a "BU" by any means (this seller is known to, let's just say, exaggerate.) And sure enough, it's clearly XF to AU Details. Paid $340 for it, and will probably return it. Still, I'd like to know what the grooves are before I do.

Thank you for any help you can provide!