My buddy has a couple plants intentionally pollinated, you can see the seeds that have developed on the selected bud sights. The plants are entering the harvest window, but is there any way to make sure the seeds are mature before harvesting without just picking a couple out and looking at them? The seeded areas are very limited due to hand pollination. So he dosn't want to waste any more than necessary.
Typically seeds that are fully mature and viable start to swell and burst the calyx. If the seed hasn't busted through the calyx yet it's probably not fully matured. You want huge seeds with black stripes for strong healthy plants. You would definitely see the seeds if they were ready. In my experience growing seeds by the time the bud is ready to harvest the seeds will almost just fall out from the bud.