Picked up a complete You Nagaba promo today. Normally the Eevee set come in packs that you can't see into but, in Japan, some collectors use a process to strip the pack down to the transparent lair. I have not been able to find another set like this being sold online at all.
Would you rip? Unfortunately we don't know if its Series 1 or 2. This is key because depending upon the series, it could be high or low numbered cards where the high numbered contains the Mantle and Jackie.
My sense is its worth more sealed because the enterprise value of it, the potential, is worth more than the risk of opening it and it being a series 1 pack.
I've always loved the mental games one goes through on vintage sealed packs or boxes and the price of it and the implied potential value.