Sealed? I can't even figure out why that's a thing. I've gotten, maybe, 10 things (of the ultra-rare variety) over the years on evilbay and always asked the seller to open it and verify before sending it. Always with the understanding the "sealed" doesn't mean nothin' to me, and that "sealed" should mean an understanding that it will be perfect when he/she opens it. Never had a problem, either. And I open my stuff before I leave the hobby shop. This doesn't help the OP with glue, but can't we have some understanding? The OP didn't keep it sealed up for 30+ years as a retirement investment. The intent was to open it and drool. Have the seller open it and drool and send proof. And, gosh, look into it if you don't know how easy it is shrink-wrap your own stuff and label it as sealed.
Mike Todd