"Looks-wise" it's a 69, but I've read from a few people on here that GM got "cheap" (surprising, huh?) and after whatever number of years they quit offering the "proper" grill insert, and just sold the 69 as a 70. The seller is probably correct that it's a NOS 70, but it's still "wrong."
That seems cheap to me (assuming you haven't ruined it and now will be outbid by another board member
) but it seems cheap enough that I would buy it and use it to bargain someone for a nice 70 grill