What value fuse is this & what does it do? (Wife's Truck!)

[rwogs]

I've been chasing down a bad ground and/or a dirty contact in my wife's 1972 C10 Pickup. While probing around, I accidentally broke a glass fuse that was inside a rubber enclosure near the fusible link and battery. I have not yet dug either end out yet, but can someone tell me what type and amperage fuse it is and what it does? I need to repair it somehow. The vehicle seems to run without it. I've borrowed a couple of images from old posts that show where the fuse/thing is.
Thanks for any help you can give.