With Twist barrels it is either a Grade 0 or 1. If the frame and lock plates are plain a Grade 0 or with a few flourishes of engraving Grade 1. Being a 12-gauge with a straight grip it is a Quality U or Quality Q.
At that time a straight grip 12-gauge was the base price for the grade. A pistol grip made it the next Quality and was $5 more. A straight grip 10-gauge was $5 more than a 12-gauge and then a pistol grip an additional $5. The 8-, 16- and 20-gauges were a lot extra --
Price List, July 1, 1882, extra.jpg