Fishing weight, my grand dad had 100s of them in all diff sizes (1/8 oz thru 2 oz). They are round so that they don't get caught in between rocks like pencil type and reg type sinkers do. They may not have used them much in your part of the country (which is why you wouldn't think it to be a sinker) but here in MI, we have a lot of rocks in certain lakes & rivers, etc. and they were used widly (mostly in the 50s and before). I still see the 'older guys' using them now and then!