Couple of easy ways.
1, if you have a pin type scale, weight the item normally (dry), they weigh it again submerged in water, say in a bucket full of water. The item tied to pin scale with a bit of fishing line, then divide the difference of the two weights into the dry weight.
2, have a graduated cylinder, a large syringe like 20 cc's from the vet should be big enough for that chain. put some water in the cylinder, note how many cc's, then put your item in and note how many cc's increase, the volume of your item. Divide the weight of the item by the cc's of volume =gm/cc or specific gravity.
Even if you did not have a graduated cylinder you could use any container with straight sides (no taper) if you can accurately measure it with verniers, and calculate the volume. You could fill the container completely full, submerge your item, then remove it, then calculate how much water is now missing.