That appears to be way too heavy for any type of iron canister shot. According to the Ordinance manuals, for example, a 2.02" diameter grape shot should average approx. 1.14 1bs in weight. A 1.17" diameter heavy canister shot (which is closest to your item's size) should average approx. 0.21 lbs, which is quite a difference from your weight. I checked weights for modern steel ball bearings and they are pretty close to the grape/canister shot weights (1 3/16" chrome steel ball bearing is 3.970 oz.)
Can you double check your diameter and weight again. For weighing, you'd need an accurate kitchen diet scale, small digital scale, or postal scale. Regular spring type scales or body digital scales are extremely inaccurate when you at the bottom end of their range.