Peter Berry, Martin Shell, M. Poorman, and other unknown makers from Dauphin County and similar schools used this style of triggerguard. Sand cast brass. Several fine rifles by Berry, Shell, Poorman, and others are shown in Thoughts on the Kentucky Rifle in its Golden Age by Joe Kindig.
Overall length is 7-9/16", inside trigger bow is 1-7/8" long, and 7/8" deep.