You dig that in a farmers field that is been plowed a-lot? Normally that's how my buttons look if i dig them in a plowed field lately. Farming equipment these days tear the crud outta relics. Good find though regardless of the condition.
Dug it on our hunting land that backs up to a battle field the soil there is almost like a thick grey sand so water is hard on things funny enough the nap sack hook was on top the ground under about 4 inches of pine needles