I have made many antler pens for hunters. My offer was give me a tine/end and the shell you used and I make the pen from that. I turn down the tine to match the end of the leaving the tine mostly untouched brown bark. I apply a solution of potassium permanganate and the white turns a lovely brown shade. The turning STINKS, LITERALLY!!!
I helped a friend for many years with the rush of dressing deer but he quit doing it because bureaucrats passed so many rules and regulations that he could not possibly follow them all.