Okay, quick update with some results: I tried the non-scientific eight-minute coin test again, just now. I used a single layer of rubylith between two sheets of glass in the lower filter position and sealed up all possible light leaks on the safelight; the safelight itself was allowed to warm up for about 20 minutes or so. After developing the test strip in complete darkness I can't see any traces of fogging or coin silhouettes...so in addition to being ecstatic at having made progress, we now know two things:
1) The rubylith layer effectively cuts the blue-green bands out and acts as an effective filter.
2) The paper emulsion is more than likely intact, which makes sense because it's being stored properly.
At this point, I think my next step is to flash the paper to its threshold and do a more accurate test, and to try installing some opaque panels in the vanes; the rubylith cuts a lot of the overall light, but it's still ridiculously bright in the darkroom and a bit less light would be appreciated when working over an enlarger easel.