I find it odd that you have to light a bomb or grenade or otherwise explosive object to see the fuse size, even as a garbage estimate as you can when inspecting piles of chyen with low per. Perhaps upon inspect/look/check with low per one could see 'long fuse' 'short fuse' 'tiny fuse' and 'massive fuse', etc. This has potential to be built on with perception as to exact measurements, or perhaps if one has a good bombs skill an estimated time amount to explosion after lighting.