Hercules (not a caveman) is Sauer's maker's mark. Don't know of any significance to multiples, probably just restamped because the first ones didn't get clean stamping. The 16_65 would probably indicate 16ga with 65mm case (approx 2.5inches). 28.5Bl is gram weight of lead shot for the service load. The other marks are 9.75 grams of Schultze Powder.