questions about 1889 shotgun

[SODBUSTER]

I BOUGHT A 10 GA 1889 SHOTGUN SERVAL YEARS AGO AND NEVER GOT IT OUT UNTIL TODAY. I KNOW NOTHING ABOUT IT AND HAVE MANY UNANWSERED QUESTIONS. WHAT IS THE CORRECT CHAMBER LENTGH ? IT HAS DEMACUS BARRELS AND HAS SOME LIGHT RUST PITTING ON THE INSIDE OF THE BARRELS. IS THIS SAFE TO SHOOT ? IF SO IS AMMO STILL AVABILE ? MY SERIAL NO IS 91075 WHEN WAS THIS MADE. HOW CAN YOU TELL WHAT CHOKE THE BARRELS ARE ? ON THE WATER TABLE THERE IS THE NUMBER 3 AND THEN A SPACE BEFORE THE SERIAL NO. WHAT DOES TIS MEAN ? WHAT COLOR DID THE BARRELS COME BLUE OR MAYBE RUST MY BLUEING IS ALL WORN OFF. THE THE SIDES BY THE HAMMERS LOOKES LIKE IT WAS CASE COLORED BUT NOW HAS SERFACE RUST ON IT. IS THERE ANY WAY TO REMOVE RUST WITHOUT DAMAGING THE CASE COLOR ? WHAT KIND OF SHELLS WERE MADE AT TIME OF MANUFACTER BRASS OR PAPER ? OTHER MARKINGS ON THE LUG ARE 40 AND 46. AD THE PROOF MARKINGS LOOK LIKE THE LETTER P WITH WHAT LOOKS LIKE A HEART LOGO AND BELOW THAT THE NUMBER 3. CAN ANY ONE TELL WHAT THAT MEANS ? WERE THESE SHOT WITH BLACK POWDER LOADS OR WAS IT SMOKELESS ? THAKS FOR ANY HELP

[2shooter]

Hi, Standard chamber for 10ga. is 2 7/8 inch.The number 3 is the grade. Number 1 being the lowest 7 being the highest.Number 1 thur 3 did not have
engraving 4 thru 7 special order with engraving.The 1897 factory catalog list number 3 having Damascus steel barrels Guaranteed for nitro powders. Your barrels should be brown damascus.They had (1897) what they called nitro or smokless and black powders.