Castle 75K on the left…98 Proto on the right 
I would need to have both masks in hand to study closely. Going off of all of the pictures ever posted on here though I would lean slightly towards the 75K Castle because of the ever so slight stretch incorporated in the sculpt. But it’s very close. Maybe Jay can send me his 98 so I can examine it closely and make a final decision.
Did you hear me Jay? 
Ha! It’s on the way Chad 
My two fav masks. I can never decide which one I like better, because tbh, I can’t tell the difference between them lol.
The only difference I can see is the noses lol
Sent from my SM-A505U using Tapatalk
I have always wanted a Castle 75k, like years now. For a while I thought maybe a PS78, but I preferred the 75k castle. Then I recently realized how close the 98 proto is and I have always thought they look very close. I’d be happy with either of them they are definitely my grail and all I have for the 78 masks are the tots H78 and a Sinister Studio Hiro I have Rowland rehaul for me. The dream is one of these beauties someday