That looks a lot like what 'Tennessee Gentleman' pods look like here.
Here's a picture I posted a few years back:
I wonder if you're seedling can be traced back to 'April Melody' which (if I'm remembering correctly) seems to be a common denominator among many of the purple podded ones.
Thomas, Chuck, and Donald;
I have been following this with some interest after I found a seedpod that looked like the attached....anyone seen this dark of seedpod? This is on one of my seedlings attachment #2. This has been on of the cooler spring/early summers in a long time, high temps in the Hi 60's to Lo 70's.