What grade could it be?

These pictures are from the seller, and I think they don't “give off” it's luster, so I'll try to describe it (I didn't make my own photos, since I don't know if I'll catch these details on my phone camera).  I think the luster is average, on a scale 1-5 being like 3.5. The cartwheel effect is here, if cartwheel itself could also be rated , I'd say 4-5. On the obverse luster overall is more dull than on the reverse, but not completly dull. On the reverse the luster is much better.

My opinion is this. Although a very nice coin, I would not place so much weight on remaining luster as it is only critical in the very highest grades of Mint State 65 and higher. Based on the photos, this coin in my opinion would grade a AU 55 to MS 60 - MS62 at best or so. It has very nice original details but It is very difficult to be precise without coin in hand. Good luck with it.

Being conservative this is an EF at best

IMO au55 -au58.

Good luck.