In the course of the last few years, I've gained some familiarity with the nuances of business strikes. Proof coins are yet an alien species. I don't know what's normal or what's unexpected. And were I to identify something unexpected, I'd then need to know is it anything special?
I did not broach the mint seal to photograph these. I hope I don't need to in order to learn. My main questions are those above. Is this degree of device duplication to be commonly expected in examining proof coins? If not, is it anything special to collectors?
According to the US Mint, proof coins are struck at least twice. I don't know if this applies to all proofs ever made, but what you are seeing could be an artifact of that. I don't see any die doubling.