It's got the squared rim. Very intricate lettering, similar to the other among Proofs I've seen. But why would someone remove it from the original Mint packaging? In possibility thinking it was a Philadelphia? And what's the value of it raw
Philadelphia didn't make any proof in 1970, would have been San Francisco. If it were a proof from San Francisco, it would be worth a couple of dollars if it weren't so heavily impaired. I'm pretty sure that you just have a nicely struck business strike from Philadelphia.
Unless of course; it's the variety. S intended for a proof no-S. Not made for frosted, but for Matte finishes. Good point tho
But it is not a proof coin. Proof coins have square rims. Those rims are anything but square. courtesy of desertgem