I would be surprised if the name is not "Everson". I had the chance to examine a fullstock rifle that was being carried through the commercial row at Friendship, which was stamped exactly as you have described. That one was definitely "Everson". That rifle had been handed down through a family in Indiana and they believed it had been made there. Since Dearborn County is very close to Friendship, Washington Everson seems likely.
The 1850 census lists Washington Everson as a gunsmith in Logan, Dearborn County Indiana. He was 49 years old, born in Pennsylvania. His wife Susan, was 45, also born in Pennsylvania. His 22 year old son John, was born in Kentucky. Five other children, Andrew, age 20; William, age 17; Sarah, age 12; Mary, age 10; and Annie, age 4, were born in Indiana. Washington Everson owned real estate valued at $500; personal estate at $250.