How to Hallmark a 0.999 Silver Straw Casting.

I did some Pine needle silver pouring today. How would you mark it 0.999 Fine Silver.pendant it is odd shaped. Would you add a small silver label? Thanks, Cliff

Hard to say without a picture, but it is sometimes possible to create a smooth surface on the back, or solder one on. Dennis.

Are you legally obliged to mark it at all in the US or is it just for your own satisfaction as a show of quality

Thanks,
Cliff